Furnace for sintering printed objects

ABSTRACT

A furnace system for printing an object using additive manufacturing. The furnace system may include a furnace chamber; an outlet fluidly coupled to the furnace chamber for removal of an exhaust gas from the furnace chamber; a conduit fluidly coupled to the outlet; an oxygen injector fluidly coupled to the conduit; an isolation system fluidly coupled to the conduit between the furnace chamber and the oxygen injector; and a catalyst enclosure comprising an oxidizing catalyst.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority of U.S. ProvisionalApplication No. 62/853,561, filed May 28, 2019, the entirety of which isincorporated by reference into this application.

DESCRIPTION Technical Field

Various aspects of the present disclosure relate generally to systemsand methods for sintering printed objects.

Background of the Disclosure

Metal injection molding (MIM) is a metalworking process useful increating a variety of metal objects. For example, a mixture of powderedmetal and one or more binders (e.g., a polymer such as polypropylene)may form a “feedstock” capable of being molded, at a high temperature,into the shape of a desired object. The initial molded part, alsoreferred to as a “green part,” may then undergo a chemical preliminarydebinding process to remove primary binder while leaving secondarybinder intact, followed by a sintering process. During sintering, thepart may be brought to a temperature near the melting point of thepowdered metal, which may thermally decompose any remaining binder andform the metal powder into a solid mass, thereby producing the desiredmetal object.

Additive manufacturing, also referred to as three-dimensional (3D)printing, includes a variety of techniques for manufacturing athree-dimensional object via a process of forming successive layers ofthe object. Three-dimensional printers may in some embodiments utilize afeedstock comparable to that used in MIM, thereby creating a green partwithout the need for a mold. The green part may then undergo debindingand sintering processes to produce the object.

In addition to MIM based additive manufacturing, there are systems usingpowder beds and loose powder, optical resin curing, and others. Manysuch methods require a furnace process to produce the final part or toenhance the properties of the part. The materials making up the part mayinclude ceramics and composites as well as metals. Additionally, thereare conventional materials that can benefit from furnace processing.

SUMMARY OF THE DISCLOSURE

Examples of the present disclosure relate to, among other things,systems and methods for sintering printed objects. Each of the examplesdisclosed herein may include one or more of the features described inconnection with any of the other disclosed examples.

According to certain aspects of the present disclosure, systems andmethods are disclosed for sintering printed objects. One embodimentprovides a furnace system comprising: a furnace chamber defining aninterior region, wherein the furnace chamber is configured to maintainan atmosphere substantially free of oxygen within the interior region;an outlet fluidly coupled to the furnace chamber for removal of anexhaust gas from the furnace chamber; a conduit fluidly coupled to theoutlet; an oxygen injector fluidly coupled to the conduit, wherein theoxidizing injector is positioned downstream of the furnace chamber andis configured to introduce an oxidizing gas into the exhaust gas; anisolation system fluidly coupled to the conduit between the furnacechamber and the oxygen injector, wherein the isolation system isconfigured to prevent a backflow of the oxidizing gas into the furnacechamber; and a catalyst enclosure comprising an oxidizing catalyst,wherein the catalyst enclosure is configured to receive a mixture of theexhaust gas and the oxidizing gas.

One embodiment provides a furnace system comprising: a furnace chamberdefining an interior region, wherein the furnace chamber is configuredto maintain an atmosphere substantially free of oxygen within theinterior region; an outlet fluidly coupled to the furnace chamber forremoval of an exhaust gas from the furnace chamber; a binder trap systemfluidly coupled to the outlet; an isolation system fluidly coupled tothe binder trap system, wherein the isolation system is positioneddownstream of the binder trap system and is configured to prevent abackflow of an oxidizing gas into the furnace chamber; a catalystenclosure comprising an oxidizing catalyst, wherein the catalystenclosure is positioned downstream of the isolation system and isconfigured to receive a mixture of the exhaust gas and the oxidizinggas; and an oxygen injector fluidly coupled to at least one of theisolation system or the catalyst enclosure, wherein the oxidizinginjector is positioned downstream of the furnace chamber and isconfigured to introduce the oxidizing gas into the exhaust gas.

One embodiment provides a furnace system comprising: a furnace chamberdefining an interior region, wherein the furnace chamber is configuredto maintain an atmosphere substantially free of oxygen within theinterior region; an outlet fluidly coupled to the furnace chamber forremoval of an exhaust gas from the furnace chamber; an isolation systemfluidly coupled to the outlet, wherein the isolation system isconfigured to prevent a backflow of an oxidizing gas into the furnacechamber; a binder cracking system fluidly coupled to the isolationsystem, wherein the binder cracking system is positioned downstream ofthe isolation system; a catalyst enclosure comprising an oxidizingcatalyst, wherein the catalyst enclosure is positioned downstream of theisolation system and is configured to receive a mixture of the exhaustgas and the oxidizing gas; and an oxygen injector fluidly coupled to atleast one of the isolation system or the catalyst enclosure, wherein theoxidizing injector is positioned downstream of the furnace chamber andis configured to introduce the oxidizing gas into the exhaust gas.

Both the foregoing general description and the following detaileddescription are exemplary and explanatory only and are not restrictiveof the features, as claimed. As used herein, the terms “comprises,”“comprising,” “including,” “having,” or other variations thereof, areintended to cover a non-exclusive inclusion such that a process, method,article, or apparatus that comprises a list of elements does not includeonly those elements, but may include other elements not expressly listedor inherent to such a process, method, article, or apparatus.Additionally, the term “exemplary” is used herein in the sense of“example,” rather than “ideal.” It should be noted that all numericvalues disclosed or claimed herein (including all disclosed values,limits, and ranges) may have a variation of +/−10% (unless a differentvariation is specified) from the disclosed numeric value. In thisdisclosure, unless stated otherwise, relative terms, such as, forexample, “about,” “substantially,” and “approximately” are used toindicate a possible variation of ±10% in the stated value. Moreover, inthe claims, values, limits, and/or ranges of various claimed elementsand/or features means the stated value, limit, and/or range +/−10%. Theterms “object,” “part,” and “component,” as used herein, are intended toencompass any object fabricated using the additive manufacturingtechniques described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate various exemplary embodiments andtogether with the description, serve to explain the principles of thedisclosed embodiments. There are many aspects and embodiments describedherein. Those of ordinary skill in the art will readily recognize thatthe features of a particular aspect or embodiment may be used inconjunction with the features of any or all of the other aspects orembodiments described in this disclosure.

FIG. 1 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 2A is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 2B depicts an exemplary isolation system, according to oneembodiment of the disclosure.

FIG. 3 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 4 is a block diagram of an exemplary furnace, system according toone embodiment of the disclosure.

FIG. 5 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 6 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 7 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 8 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 9A is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 9B is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 9C is a block diagram of part of the exemplary furnace system ofFIG. 9B, according to one embodiment of the disclosure.

FIGS. 9D-9F depict exemplary data plots related to the part of theexemplary furnace system of FIG. 9C.

FIG. 10 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 11 is a block diagram of an exemplary furnace system, according toone embodiment of the disclosure.

FIG. 12A is a block diagram of an additive manufacturing systemaccording to some embodiments of the disclosure.

FIG. 12B illustrates an exemplary printing subsystem of the system ofFIG. 12A.

FIG. 12C illustrates an exemplary debinding subsystem of the system ofFIG. 12A.

FIG. 13A is a block diagram of an additive manufacturing systemaccording to some embodiments of the disclosure.

FIG. 13B illustrates an exemplary printing subsystem of the system ofFIG. 13A.

FIG. 13C illustrates another exemplary printing subsystem of the systemof FIG. 13A.

FIG. 14 depicts an exemplary computer device or system, in whichembodiments of the present disclosure, or portions thereof, may beimplemented.

DETAILED DESCRIPTION

Embodiments of the present disclosure include systems and methods tofacilitate and improve the efficacy and/or efficiency of sinteringprinted objects. Reference now will be made in detail to examples of thepresent disclosure described above and illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

An additive manufacturing process may produce an initial “green”(unsintered) part, e.g., a printed part, which may undergo furtherprocessing to generate a finished part. This processing may includedebinding, such as any combination of chemical debinding (i.e., removingvarious binder components through the use of solvents), reactivedebinding (i.e., exposing the parts to material, such as a gas, thatreacts or causes a reaction with binder components(s) or other materialspresent in the part or with the metal or other particles that make upthe part to cross-link or otherwise render the binder components orother materials more easily removed), and/or thermal debinding (i.e.,utilizing heat to evaporate or decompose binder components and othermaterials present within the part). In some instances, the furtherprocessing may be a sintering process.

A sintering process, in the context of the current disclosure, refers towhen a part is heated in a furnace chamber to bring its temperature nearthe melting point of the powdered metal. As the green part is heated, insome embodiments, thermal debinding may first occur, during which anyremaining binder components may be thermally decomposed (hereinafterreferred to as a “thermal debinding process”). Then, as the part isheated to just below the melting point of the metal powder from which itis formed, the metal powder may densify into a solid mass (hereinafterreferred to as a “main sintering process”), thereby producing thefinished part. As used herein, “sintering process” may refer to heatinga part in a furnace chamber, which may include thermal debinding, mainsintering, or both. Any sintering process or furnace process may beutilized with respect to the embodiments disclosed herein. The sinteringprocess may produce a gaseous effluent, particularly during thermaldebinding, which may be pumped out of the furnace chamber and directedthrough an exhaust channel. In some embodiments, the gaseous effluentmay include the volatilized binder components generated during thethermal debinding process. In some instances, the gaseous effluent mayinclude hydrocarbons, carbon monoxide, hydrogen and/or other gases thatmay be harmful in certain conditions.

Conventional methods of filtering such gaseous effluents produced duringa sintering process within a furnace chamber are generally not suitablefor an office environment where air quality in the office and localoutdoor environments have stringent standards. As such, there is a needfor an improved method of filtering gaseous effluents produced during asintering process and for controlling the sintering process accordingly.

Embodiments of the present disclosure may address one or more of theseproblems, or address other aspects of the prior art.

FIG. 1 is a block diagram of a furnace system 100 according to exemplaryembodiments. The furnace system 100 may include a furnace chamber 102,an isolation system 104, an oxidizing gas source 106, an air injector109 (also referred to as an oxygen injector, which may introduce air oroxygen gas into the system), a catalytic converter system 110, a COdetector 112, one or more pressure regulated gas sources 114, acontroller 116, and a power source 118. The furnace system 100 mayfurther include various thermocouples, valves, pressure gauges, and massflow controllers (MFCs), as will be described in further detail below.

The furnace chamber 102 may be a sealable and insulated chamber designedto enclose a controlled atmosphere substantially free of oxygen toprevent combustion. In the context of the current disclosure, acontrolled atmosphere refers to an atmosphere being controlled for oneor more of temperature, composition, and pressure. In the context of thecurrent disclosure, an atmosphere substantially free of oxygen refers toan atmosphere that is free of oxygen or has levels of oxygen below apredetermined threshold amount of oxygen. For example, the predeterminedthreshold amount of oxygen may be, e.g., about 100 ppm of oxygen orless, for example, about 10 ppm or about 50 ppm of oxygen. In someembodiments, the atmosphere substantially free of oxygen may includeinert gases, such as argon and/or nitrogen.

The furnace chamber 102 may include one or more heating elements 122 forheating the atmosphere enclosed within the furnace chamber 102. Althoughtwo heating elements 122 are depicted in FIG. 1, any suitable number ofheating elements may be used. In some embodiments, the controller 116may be configured to draw power from the power source 118 to heat theheating elements 122 in accordance with a predetermined heating profilefor the furnace chamber 102. In some embodiments, the power source 118may be an electrical power source (e.g., single phase analog current,three phase analog current, or direct current power source). Controller116 may also be operably coupled to one or more thermocouples and/orpressure gauges and/or other components within the furnace system 100 tomeasure and/or control conditions within the furnace chamber 102. Forexample, a part 126 may be placed within the furnace chamber 102 for asintering process. As part of the thermal debinding process, the furnacechamber 102 may be heated to a suitable temperature in order to degradeany binder components included in the part 126. In some instances, thefurnace chamber 102 may be heated up to about 370 degrees Celsius or toabout 500 degrees Celsius during the thermal debinding process, by whichany binder components included in the part 126 may be volatilized.

As shown in FIG. 1, the furnace chamber 102 may include a retort 124 inwhich the part 126 is placed for a sintering process. In someembodiments, the retort 124 may include heat-conductive walls (e.g.,graphite walls) to spread heat generated by the heating elements 122within the furnace chamber 102, thereby enhancing temperature uniformityin a region where the part 126 is located. In some embodiments, theretort may 124 include a graphite box with walls partially or fullyenclosing the region where the part 126 is located. In such embodiments,the retort 124 may be utilized as a microwave applicator.

In some embodiments, the controller 116 may be configured to control theatmosphere within the furnace chamber 102, such as the pressure and/ortemperature within the furnace chamber 102. For example, the pressurewithin the furnace chamber 102 may be atmospheric, positive, or negative(e.g., a vacuum). In some embodiments, the atmospheric pressure may beup to 3 psi. In some embodiments, the atmospheric pressure may behigher, depending on the composition of the part 126 being processedwithin the furnace chamber 102.

As shown in FIG. 1, the furnace system 100 may include a controller 116,which may be operably connected to the various components included inthe furnace system 100. In some embodiments, the controller 116 may beconfigured to control one or more processes, e.g., a thermal debindingprocess and main sintering process (e.g., densification), in the furnacesystem 100. In some embodiments, the controller 116 as described hereinmay be configured to control one or more processes in the variousfurnace systems disclosed herein, including furnace systems 200-1100. Insome embodiments, the various components or subsets of componentsincluded in the furnace system 100 (or furnace systems 200-1100) may bein communication with one or more controllers, to which the controller116 may be operably connected to. In such embodiments, the one or morecontrollers in addition to, or as an alternative to, the controller 116may be configured to control one or more processes, e.g., a thermaldebinding process and main sintering process (e.g., densification), inthe furnace system 100 (or furnace systems 200-1100). In someembodiments, the one or more controllers in addition to, or as analternative to, the controller 116 may be configured to control one ormore processes in the various furnace systems disclosed herein.

Gaseous effluent may be released into the atmosphere of the chamber 102as the part 126 is heated during the sintering process, e.g., during thethermal debinding process. In some embodiments, the gaseous effluent maybe pumped out of the furnace chamber 102, flowed through the isolationsystem 104, and directed towards the catalytic converter system 110. Theisolation system 104 may be configured to prevent any downstream fluid(e.g., gas, particularly oxygen gas) from flowing back towards thefurnace chamber 102. In some embodiments, the isolation system 104 maycomprise a vacuum pump, a venturi pump, or other suitable pumpconfigured to pump this gaseous effluent from the furnace chamber 102via one or more furnace exhaust conduits 103 through the isolationsystem 104. The gaseous effluent may then be directed towards thecatalytic converter system 110 to remove volatilized binder componentand/or other toxic fumes from the gaseous effluent.

In some embodiments, the furnace system 100 may include the air injector109 as shown in FIG. 1. The air injector 109 may provide air injectionfrom the oxidizing gas source 106. The oxidizing gas that flows throughthe air injector 109 may be directed towards the catalytic convertersystem 110. The oxidizing gas may be mixed with the gaseous effluent (aprocess also referred to as diluting the gaseous effluent) and directedtowards the catalytic converter system 110. Although the furnace chamber102 may need to be maintained at an atmosphere substantially free ofoxygen, the catalytic converter system 110 needed to remove volatizedbinder component from the gaseous effluent may require oxygen tofunction properly. Accordingly, to achieve an office-safe furnace system100, oxygen may actually need to be introduced into the system and mixedwith the gaseous effluent before introduction into the catalyticconverter system 110. As such, the catalytic converter system 110 mayalso be referred to as an oxidizing catalytic converter. In someembodiments, the oxidizing gas may be added to the catalyst enclosed inthe catalytic converter system 110 when the temperature of the catalyticconverter system 110 meets or exceeds a threshold temperature. Theoxidizing gas flowing through the catalyst may remove excess heat andmay cool the catalytic converter system 110. In some embodiments, theair injector 109 may be an air pump, an air compressor, and/or acompressed air source (e.g., bottled gas). Air injector 109 mayintroduce air, pure oxygen, or a mixture of oxygen and other gases intothe system.

The catalytic converter system 110 may be configured to catalyzereactions to decompose various compounds in the furnace chamber 102exhaust, i.e., the gaseous effluent, to safer compounds, such as waterand CO₂. In some embodiments, catalytic converter system 110 may beconfigured to combust volatilized binder components present in thegaseous effluent. In some embodiments, during the sintering cycle,carbon monoxide (CO) may be produced by the reduction of metal oxideswith carbon in the metal. The catalytic converter system 110 may beconfigured to convert this CO to CO₂. The catalytic converter system 110may use oxidizing gas to combust volatilized binder components and/oroxidize CO present in the gaseous effluent. For example, the oxidizinggas provided by the air injector 109 may be used to combust volatilizedbinder components and/or oxidize CO present in the gaseous effluent.

In some embodiments, the catalytic converter system 110 may include acatalyst enclosure 111 a and a catalyst heater 111 b. In someembodiments, the catalyst heater 111 b may be used to pre-heat thecatalyst contained in the catalyst enclosure 111 a before a sinteringprocess in the furnace chamber 102. The catalyst contained in thecatalyst enclosure 111 a may generate heat when it reacts with thecompounds in the furnace exhaust. As such, the catalyst heater 111 b maycease heating the catalyst once the catalyst begins to react to thecompounds in the gaseous effluent. In some instances, the catalyst maybecome overheated. In such instances, the sintering process in thefurnace chamber 102 may be stopped. Additional methods of adjusting thetemperature of overheated catalyst are described in further detail withreference to FIG. 11 below.

The isolation system 104 may be configured to prevent oxidizing gas fromthe oxidizing gas source 106 from flowing back into the furnace chamber102. Specifically, the isolation system 104 may be configured to preventoxidizing gas directed to and used in the catalytic converter system 110from flowing back into the furnace chamber 102. As described above, thefurnace chamber 102 maintains a controlled atmosphere substantially freeof oxygen within the chamber in order to prevent combustion within thefurnace chamber 102.

In some embodiments, the isolation system 104 may comprise a vacuumpump, as described above, to pump gaseous effluent from the furnacechamber 102 via one or more furnace exhaust conduits 103 through theisolation system 104 and towards the catalytic converter system 110. Insome embodiments, the vacuum pump may include a ballast to provide anair injection from the oxidizing gas source 106. In such embodiments, anoxidizing gas may be directed to the vacuum pump, e.g., to a pumpchamber or a discharge port of the vacuum pump, through a ballast port.In some embodiments, the gaseous effluent flowing out of the vacuum pumpexhaust towards the catalytic converter system 110 may include pump oil.In some embodiments, the furnace system 100 may comprise a demisterpositioned adjacent to the vacuum pump exhaust. In such embodiments, thedemister may be configured to remove and drain the pump oil back to thevacuum pump. Without the demister, the pump oil present in the gaseouseffluent may enter the catalytic converter system 110, which may clogthe catalytic converter system 110 and cause the enclosed catalyst tooverheat. Further, the continuous loss of the pump oil may cause thevacuum pump to run dry and cause the vacuum pump to overheat. Anembodiments of the vacuum pump and the demister is described in furtherdetail below with reference to FIG. 11.

In some embodiments, the isolation system 104 may be configured tocapture, neutralize, and/or chemically convert (hereinafter collectivelyreferred to as “trap”) one or more compounds of the gaseous effluent.For example, the isolation system 104 may trap at least a portion of thevolatilized binder components present in the gaseous effluent. Variousembodiments of the isolation system 104 are described in further detailbelow with reference to FIGS. 2-10. In some embodiments, the furnacesystem 100 may further comprise a binder trap system, as described infurther detail below with reference to FIGS. 6-8. In some embodiments,the furnace system 100 may further comprise a binder cracking system, asdescribed in further detail below with reference to FIG. 5.

The pressure regulated gas source 114 may provide one or more gases tothe furnace chamber 102 through a gas inlet 115 fluidly connected to thefurnace chamber 102. In some embodiments, the one or more gases mayinclude Ar, N₂, forming gases (e.g., a non-explosive mixture of Ar—H₂ orN₂—H₂), CO₂, and/or air. In some embodiments, the gas inlet 115 mayinclude a mass flow controller (MFC) 113 for controlled input of one ormore gases to the furnace chamber 102. In some embodiments, there may bemore than one pressure regulated gas source, each fluidly connected tothe furnace chamber 102. Each of pressure regulated gas sources maycomprise one or more dedicated gas inlets and MFCs. The furnace pressuremay be controlled on the outlet side of furnace chamber 102. Forexample, the user may set the input flow via the MFC and the inletpressure at the regulator. The regulator pressure may be set so that ifthe outlet becomes inoperative (e.g., clogged), the furnace may notover-pressurize to an unsafe condition. In some embodiments, forexample, the furnace chamber may comprise a ceramic tube furnacechamber. In such embodiments, a regulator pressure may be set to 3 PSIfor the pressure regulated gas source 114. In some embodiments, thefurnace chamber may comprise a metal walled furnace chamber. In suchembodiments, a regulator pressure may be set to 10 PSI for the pressureregulated gas source 114. In some embodiments, a regulator pressure maybe set to more than 30 PSI for the pressure regulated gas source 114.The CO detector 112 may be located at an outlet of the catalyticconverter system 110. The CO detector 112 may be communicativelyconnected to the controller 116 and may be used to monitor CO flowingout of the furnace system 100. In some embodiments, controller 116 maybe configured to shut down the furnace system 100 if the CO detector 112detects CO or detects an amount of CO that meets or exceeds a thresholdsafety value. In some embodiments, an alarm may be initiated if COdetector 112 detects CO or detects an amount of CO that meets or exceedsa threshold value. Although a CO detector 112 is shown in FIG. 1, itshould be recognized that any type of detector or combination ofdetectors or number of detectors may be included in furnace system 100(or furnace systems 200 through 1100) to confirm that gaseous exhaustexiting furnace system 100 (or furnace systems 200 through 1100) meetsair quality safety standards to promote a safe environment aroundfurnace system 100.

In some embodiments, the furnace system 100 (or furnace systems 200through 1100) may include an O₂ sensor located at the outlet of thecatalytic converter system 110. The O₂ sensor may be communicativelyconnected to the controller 116 and may monitor excess O₂ flowing out ofthe furnace system 100. In some embodiments, the gas flow within thefurnace system 100 may be reconfigured based on the monitored O₂ level.For example, reaction air flow from pressure-regulated gas source 114may be set to target correct values for excess O₂ or a minimum setting.In some embodiments, a monitored excess O₂ level flowing out of thefurnace system 100 may indicate that there is no CO flowing out of thefurnace system 100 or that there is less CO flowing out of the furnacesystem 100.

In some embodiments, the furnace system 100 (or furnace systems 200through 1100) may include a hydrocarbon sensor located at the outlet ofthe catalytic converter system 110. The hydrocarbon sensor may becommunicatively connected to the controller 116. In some embodiments,controller 116 may be configured to shut down the furnace system 100 ifthe hydrocarbon sensor detects hydrocarbon or detects an amount ofhydrocarbon that meets or exceeds a threshold value. In someembodiments, an alarm may be initiated if hydrocarbon sensor detectshydrocarbon or detects an amount of hydrocarbon that meets or exceeds athreshold value.

FIG. 2A is a block diagram of a furnace system 200 according to oneembodiment. Similar components in FIG. 2A may function similarly to whatis described in reference to corresponding components in FIG. 1. Asshown in FIG. 2A, the isolation system 104 may include a liquid bubbler202. In this embodiment, the oxidizing gas source 106 may be fluidlyconnected via MFC2 to a conduit 206 between the isolation system 104 andthe catalytic converter system 110. In some embodiments, the oxidizinggas source 106 may direct oxidizing gas towards the catalytic convertersystem 110 using a vacuum pump and/or the air injector 109, as describedin reference to FIG. 1.

The liquid bubbler 202 may isolate the furnace chamber 102 from theoxidizing gas source 106 (e.g., a blower or compressed air) as describedin further detail below with reference to FIG. 2B. FIG. 2B shows anexpanded view of the liquid bubbler 202 of FIG. 2A according to oneembodiment. The liquid bubbler 202 may include a first chamber 210 a, asecond chamber 210 b, the furnace exhaust conduit 103, a connectingconduit 204 between the first and second chambers 210 a-b, and an outletconduit 206 from the second chamber 210 b. The second chamber may be 210b partially filled with a liquid 218 to a certain height, H. In someembodiments, the liquid 218 may include an oil or other non-volatileliquid. For example, the liquid 218 may be a low vapor pressure liquid,such as hydrocarbon or silicone pump oils of diffusion pump oils. Theliquid 218 may be an oil with a density of approximately 0.9 to 1.1g/cc. As another example, the liquid 218 may be a liquid metal, e.g.,liquid tin. In yet another example, the liquid may be liquid salt.

The liquid bubbler 202 may be configured to maintain a pressuredifference P across the liquid bubbler 202 proportional to the height(H) of the liquid 218, the liquid density (rho), and gravitationalconstant (g), where P=rho·g·H. As an example, an oil with a density ofapproximately 0.9 to 1.1 g/cc and a liquid height of 10 cm may provide apressure drop of about 100 Pa or about 0.014 PSI.

The furnace exhaust conduit 103 may be fluidly connected to an upperregion of the first chamber 210 a. The gaseous effluent evacuated fromthe furnace chamber 102 may be directed into the first chamber 210 athrough the furnace exhaust conduit 103. The furnace exhaust conduit 103may be heated in order to prevent any condensation of high molecularweight species in the volatilized binder components present in thegaseous effluent.

The connecting conduit 204 may include two ends, a first end 212 a whichextends into the first chamber 210 a and a second end 212 b whichextends into the second chamber 210 b. In use, the first end 212 a maydraw in the gaseous effluent contained in the first chamber 210 a. Thesecond end 212 b may allow the gaseous effluent drawn in from the firstchamber 210 a to flow into the second chamber 210 b. The second end 212b may be positioned below a top surface of the liquid 218. For example,the second end 212 b may be located in a central region or in a lowerregion of the second chamber 210 b, as shown in FIG. 2B. The height, H,of the liquid 218 may be several times larger, e.g., at least 10 timeslarger, than the diameter of a gas bubble formed by the gaseous effluentbubbling through the liquid 218. In some embodiments, the liquid 218 maybe approximately half the height of the second chamber 210 b or morethan half the height of the second chamber 210 b. The first end 212 amay be located near the bottom of the first chamber 210 a such that inthe event that the liquid 218 is sucked back into the first chamber, thevapor seal is maintained.

The liquid 218 in the second chamber 210 b may effectively seal againstbackflow of oxidizing gas that may be introduced into the furnace system200 further downstream of the liquid bubbler 202, preventing oxidizinggas from entering the furnace chamber 102. The volume of liquid 218 inthe second chamber 210 b should be less than the volume of the firstchamber 210 a in order to prevent liquid 218 from being sucked out ofthe second chamber 210 b, through the first chamber 210 a, and back intothe upstream portion of the furnace system 200 in the event that inletgas flow into the furnace chamber 102 via the gas inlet conduit 115 isstopped during furnace cooling.

The outlet conduit 206 may be located above the top surface of theliquid 218. In some embodiments, the outlet conduit 206 may be fluidlyconnected to the top or to an upper region of the second chamber 210 b.In some embodiments, a splash guard 222 may be located between theoutlet conduit 206 and the surface of the liquid 218 such that bubblingliquid 218 does not get trapped in the outlet conduit 206 and pushed outof the second chamber 210 b further downstream in the furnace system200. In some embodiments, a low density floating granular media, e.g.,plastic pellets, rubber, hollow glass, graphite, and/or metal spheres,may be disposed on the top surface of the liquid 218 to reduce thesplashing of oil droplets instead of, or in addition to, the splashguard 222. In some embodiments, the low density floating granular mediamay have a density lower than that of the liquid 218.

In some embodiments, the first chamber 210 a may be utilized as a bindertrap. That is, the first chamber 210 a may be used to trap volatilizedbinder components present in the gaseous effluent. In such embodiments,the liquid bubbler 202 may include a first cooler 220 a configured tocool the first chamber 210 a. The first chamber 210 a may include atortuous conduit with one end fluidly connected to the furnace exhaustconduit 103 and another end fluidly connected to the connecting conduit204. The first cooler 220 a may be configured to cool the first chamber210 a and the gaseous effluent coming through the furnace exhaustconduit 103 as it is passed through the tortuous conduit such that theeffluent is chilled, and the volatilized binder components included inthe effluent condenses and/or coalesces. In some embodiments, thecondensed and/or coalesced binder components may be heated and drainedout. For example, melted wax binder may be melted and then allowed todrain out. In some embodiments, the tortuous conduit may comprise ametal wool mesh, e.g., stainless steel or copper. In such embodiments,the condensed and/or coalesced binder components may be collected on asurface area of the metal wool mesh. The mesh may be removed, e.g.,between furnace processes, and the collected binder components may beremoved from the mesh. In some instances, the collected bindercomponents may be removed using a solvent. In some embodiments, the meshmay be reattached after removing the binder components.

In some embodiments, the liquid 218 in the second chamber 210 b mayserve as a binder trap to collect higher molecular weight volatilizedbinder components, e.g., when an oil is used as the liquid 218. When thegaseous effluent comes into contact with the liquid 218, the gas maycool, thereby causing the volatilized binder components to condense. Insome embodiments, volatilized binder components with higher molecularweight may form a miscible solution with certain oils. As such, theliquid bubbler 202 may collect a sufficient amount of volatilized bindercomponents present in the gaseous effluent. In some embodiments, thecollected volatilized binder components may collect in second chamber210 b, increasing the height of the fluid in second chamber 210 b. Insuch embodiments, fluid may be removed from the second chamber 210 bperiodically. A cooler 220 b may be used to cool the second chamber 210b, particularly if large amounts of gaseous effluent is flowed throughthe liquid bubbler 202, to facilitate use of second chamber 210 b as abinder trap.

In some embodiments, the liquid 218 in the second chamber 210 b mayserve as a binder cracking enclosure when a liquid metal or a liquidsalt is used as the liquid 218. In such embodiments, the liquid 218 inthe second chamber 210 b may be heated such that the heated liquid 218causes volatilized binder components present in the gaseous effluent tobreak down to a lower molecular weight species and expand in volume,which may create carbon residue. In such embodiments, not as manyvolatilized binder components may be collected in the second chamber 210b. In some instances, none of the volatilized binder components may becollected in the second chamber 210 b.

Referring back to FIG. 2A, an exemplary process for pressure control andcatalyst temperature control with reference to the furnace system 200 isdescribed below. In some embodiments, the controller 116 may control theexemplary process for pressure control and catalyst temperature controlas follows. As shown in FIG. 2A, the furnace system 200 may include oneor more pressure gauges P0, P1, P2, and P3 for monitoring and/orcontrolling the pressure throughout the furnace system 200. The furnacesystem 200 may further include one or more thermocouples TC1, TC2, andTC3 for monitoring and/or controlling the temperature throughout thefurnace system 200. The furnace system 200 may also include a mass flowcontroller 1 (MFC1), which may adjustably control the inlet gas flowinto the furnace chamber 102, and MFC2, which may adjustably control theamount of oxidizing gas introduced into the furnace system 200. It willbe understood that although four pressure gauges and thermocouples, andtwo mass flow controllers are depicted in given locations, any suitablenumber and arrangement of pressure gauges, thermocouples, and mass flowcontrollers may be included in the furnace system 200.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially, agas inlet pressure may be set at P0 either manually or by controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The liquid bubbler 202 of isolation system 104may prevent or mitigate pressure build up within the furnace system 200during a sintering process as long as the liquid 218 contained withinthe liquid bubbler 202 does not collect too many binder components. Insome instances, when there are too many binder components contained inthe liquid 218, the liquid may become viscous and/or may form a gel-likesubstance. This may clog the various conduits associated with the liquidbubbler 202, e.g., the furnace exhaust conduit 103, the connectingconduit 204, and/or the outlet conduit 206. In some embodiments, thepressures at P1, P2, and P3 may be monitored, e.g., manually or by thecontroller 116, and processing performed within the furnace system 200may be stopped if the pressure at one or more of P1, P2, and P3 exceedsor falls below one or more predetermined thresholds. In someembodiments, the pressures at P1 and P2 may be maintained asapproximately equal. In the context of the current disclosure, about a0.5 PSI pressure difference in the pressure at P1 and P2 may beconsidered as approximately equal. There may be a pressure drop at P3such that the pressure at P3 is lower that the pressure at P1 and P2.For example, the pressure at P1 and P2 may be 2-3 PSI and the pressureat P3 may be 0-2 PSI. As another example, the pressure at P1 and P2 maybe 1-3 PSI and the pressure at P3 may be 0-1 PSI. In some instances thepredetermined pressure threshold for the pressure at P1 and P2 may be 3PSI. In such instances, the furnace chamber 102 may comprise a ceramicfurnace chamber. In some instances the predetermined pressure thresholdfor the pressure at P1 and P2 may be 10 PSI. In such instances, thefurnace chamber 102 may comprise a metal furnace chamber. In someembodiments, an alarm may be initiated if the pressure at one or more ofP0, P1, P2, and P3 exceeds or falls below one or more predeterminedthresholds.

With respect to catalyst temperature control, the furnace system 200 maybe configured to try to achieve a substantially constant temperature atTC2. That is, the temperature of the catalyst contained in the catalystenclosure 111 a should be maintained at a constant temperature range. Insome embodiments, the temperature at TC2 may be maintained within arange of 285-600 degrees Celsius. In some embodiments, the temperatureat TC2 may depend on the catalyst contained in the catalyst enclosure111 a. The catalyst heater 111 b may control an adjustable setpoint atTC1 based on the monitored temperature feedback from TC2. In someembodiments, the adjustable setpoint at TC1 may be within a range of225-425 degrees Celsius. If TC2 meets or exceeds the setpoint (i.e., ifthe catalyst becomes overheated) the following steps may be performed:(1) the catalyst heater 111 b may be turned off; (2) the oxidizing gasflow from the oxidizing gas source 106 through MFC2 may be increased;and/or (3) the inlet gas flow through MFC1 may be decreased. Theincreased oxidizing gas flow may cool the catalyst such that thecatalyst stays below a maximum temperature. In some embodiments, if theCO detector 112 (or other detector(s)) detects CO, or detects an amountof CO that meets or exceeds a threshold value, then MFC1, MFC2, and/orpower to the one or more heating elements 122 may be shut off. In someembodiments, an alarm may be initiated if the CO detector 112 detects COor detects an amount of CO that meets or exceeds a threshold value. Insome embodiments, a heater for the furnace exhaust conduit 103 may becontrolled based on a temperature measured at TC3. In some embodiments,the temperature at TC1, TC2, and TC3 may be monitored by the controller116 or manually, and processing performed within the furnace system 200may be stopped if the temperature at one or more of TC1, TC2, and TC3exceeds or falls below one or more predetermined thresholds. In someembodiments, an alarm may be initiated if the temperature at one or moreof TC1, TC2, and TC3 exceeds or falls below one or more predeterminedthresholds.

FIG. 3 is a block diagram of a furnace system 300 according to oneembodiment. Similar components shown in FIG. 3 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A, and 2B. As shown in FIG. 3, the isolationsystem 104 may include a check valve 302 (also referred to as a one-wayvalve). In this embodiment, the oxidizing gas source 106 may be fluidlyconnected via MFC2 to a conduit 306 extending between the isolationsystem 104 and the catalytic converter system 110. In some embodiments,the oxidizing gas source 106 may direct oxidizing gas towards thecatalytic converter system 110 using a vacuum pump and/or the airinjector 109, as described in reference to FIG. 1.

The check valve 302 may be configured to isolate the furnace chamber 102from the oxidizing gas source 106 (e.g., a blower or compressed air).The check valve 302 may be configured to maintain a pressure differenceacross the check valve 302 and to prevent back diffusion of oxidizinggas into the furnace chamber 102. In some embodiments, the check valvemay provide a pressure drop of about ⅓ PSI to about 10 PSI. In someembodiments, the furnace system 300 may comprise an atmospheric furnace.In such embodiments, low pressures, e.g., pressure up to 3 PSI, may beused.

Both the furnace exhaust conduit 103 and the conduit 306 may be heatedin order to prevent or reduce condensation of high molecular weightspecies in the volatilized binder components contained within thegaseous effluent from furnace chamber 102. MFC1 may be configured toadjustably control the gas inlet such that a sufficient quantity ofnon-reactive gas is present in the gaseous effluent. In someembodiments, a sufficient quantity of non-reactive gas may refer to asufficient proportion of non-reactive gas present in the gaseouseffluent that is able to bring the gaseous effluent below a lowerexplosive limit (LEL). The mixture of the non-reactive gas, thevolatilized binder effluent, and the oxidizing gas do not form anexplosive or self igniting mixture before entering the catalyticconverter system 110. In some embodiments, the conduits, e.g., thefurnace exhaust conduit 103 and the conduit 306, may be sizedappropriately so that pressure buildup is reduced or minimized. During athermal debinding process for a part 126 in the furnace chamber 102,most of the gaseous flow within the furnace system 300 may depend on theinert gas introduced through the gas inlet conduit 115 via MFC1.Accordingly, there may not be much fluctuation in the total flow rate ofgas in the furnace system 300 during the thermal debinding process.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 300 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 3, the furnace system 300 may include one or more pressuregauges P0, P1, P2, P3, and P5 for monitoring and/or controlling thepressure throughout the furnace system 300. The furnace system 300 mayfurther include one or more thermocouples TC1, TC2, TC3, and TC4 formonitoring and/or controlling the temperature throughout the furnacesystem 300. The furnace system 300 may also include MFC1, which mayadjustably control the inlet gas flow in to the furnace chamber 102, andMFC2, which may adjustably control the amount of oxidizing gasintroduced into the furnace system 300. It will be understood thatalthough five pressure gauges, four thermocouples, and two mass flowcontrollers are depicted in given locations, any suitable number andarrangement of pressure gauges, thermocouples, and mass flow controllersmay be included in the furnace system 300.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially, agas inlet pressure may be set at P0 either manually or by controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The pressure at P1 and P2 may be maintained asapproximately equal. In the context of the current disclosure, about a0.5 PSI pressure difference in the pressure at P1 and P2 may beconsidered as approximately equal. The pressure at P3 may be less thanat P2 due to leak pressure of the check valve 302. The pressure controlwithin furnace system 300 may be primarily controlled via MFC2 and MFC1in some embodiments. The conduits may be sized appropriately so thatthere is no significant pressure buildup as oxidizing gas from MFC2 ismixed with effluent. If the pressure at P1, P2, or P3 is over apredetermined safety threshold, then the gas flow through MFC2 and/orMFC1 may be decreased. In some embodiments, the flow of gas through MFC2may be decreased first and then the flow through MFC1 may be decreased.In some embodiments, the pressures at P0, P1, P2, P3, and P5 may bemonitored by the controller 116 or manually, and processing performedwithin the furnace system 300 may be stopped or gas flow through MFC2and/or MFC1 may be reduced or stopped if the pressure at one or more ofP0, P1, P2, P3, and P5 exceeds or falls below one or more predeterminedthresholds. In some embodiments, an alarm may be initiated if thepressure at one or more of P0, P1, P2, P3, and P5 exceeds or falls belowone or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 300 maybe configured to try to achieve a substantially constant temperature atTC2. That is, the temperature of the catalyst contained in the catalystenclosure 111 a may be maintained at a substantially constanttemperature range. In some embodiments, the temperature at TC2 may bemaintained within a range of 285-600 degrees Celsius. In someembodiments, the temperature at TC2 may depend on the catalyst containedin the catalyst enclosure 111 a. The catalyst heater 111 b may beconfigured to control the adjustable setpoint at TC1 based on themonitored temperature feedback from TC2. In some embodiments, theadjustable setpoint at TC1 may be within a range of 225-425 degreesCelsius. If the temperature at TC2 meets or exceeds the setpoint (i.e.,if the catalyst becomes overheated) the following steps may beperformed: (1) the catalyst heater 111 b may be turned off; (2) theoxidizing gas flow from the oxidizing gas source 106 through MFC2 may beincreased; and/or (3) the inlet gas flow through MFC1 may be decreased.In some embodiments, if the CO detector 112 detects CO, or detects anamount of CO that meets or exceeds a threshold value, then an alarm maybe initiated. In some embodiments, upon CO detection, MFC1 and/or powerto the one or more heating elements 122 may be shut off while MFC2remains open to provide backpressure on the check valve 302 and thefurnace chamber 102. In some embodiments, one or more heaters for thefurnace exhaust conduit 103 and/or conduit 306 may be controlled basedon temperatures measured at TC3 and/or TC4. In some embodiments, thetemperatures at TC1, TC2, TC3, and TC4 may be monitored by thecontroller 116 or manually, and processing performed within the furnacesystem 300 may be stopped if the temperature at one or more of TC1, TC2,TC3, and TC4 exceeds or falls below one or more predeterminedthresholds. In some embodiments, an alarm may be initiated if thetemperature at one or more of TC1, TC2, TC3, and TC4 exceeds or fallsbelow one or more predetermined thresholds.

FIG. 4 is a block diagram of a furnace system 400 according to oneembodiment. Similar components shown in FIG. 4 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, and 3. As shown in FIG. 4, the isolationsystem 104 may include a check valve 302 and a venturi pump 402. In thisembodiment, the oxidizing gas source 106 may be fluidly connected viaMFC2 to the venturi pump 402. The oxidizing gas source 106 may also befluidly connected via MFC3 to a conduit 406 b between the venturi pump402 and the catalytic converter system 110. In some embodiments, theoxidizing gas source 106 may direct oxidizing gas towards the catalyticconverter system 110 using a vacuum pump and/or the air injector 109, asdescribed in reference to FIG. 1.

As described with reference to FIG. 3, the check valve 302 may beconfigured to isolate the furnace chamber 102 from the oxidizing gassource 106 (e.g., a blower or compressed air). The check valve 302 maybe configured to maintain a pressure difference across the check valve302 and to prevent back diffusion of oxidizing gas into the furnacechamber 102. In some embodiments, the check valve 302 may provide apressure drop of about ⅓ PSI to about 10 PSI. In some embodiments, thefurnace system 400 may comprise an atmospheric furnace. In suchembodiments, low pressures, e.g., pressure up to 3 PSI, may be used.

One or more of the furnace exhaust conduit 103, a conduit 406 a betweenthe check valve 302 and the venturi pump 402, and conduit 406 b may beheated in order to prevent condensation of high molecular weight speciesin the volatilized binder components present in the gaseous effluent.MFC1 may be configured to adjustably control the gas inlet such that asufficient quantity of non-reactive gas is present in the gaseouseffluent. In some embodiments, a sufficient quantity of non-reactive gasmay indicate a proportion of the non-reactive gas present in the gaseouseffluent to bring the gaseous effluent below the explosive limit (LEL).The mixture of the non-reactive gas, the volatilized binder effluent,and the oxidizing gas do not form an explosive or self igniting mixturebefore entering the catalytic converter system 110.

The venturi pump 402 may be located at the point of the oxidizing gasinlet and may be configured to utilize the oxidizing gas provided by theoxidizing gas source 106 to draw gas and pull the gaseous effluent fromthe check valve 302. As such, the venturi pump 402 may prevent backpressure on the check valve 302 and the furnace chamber 102. As shown inFIG. 4, separate MFC2 and MFC3 may provide separate oxidizing gas flowsto the venturi pump 402 and the conduit 406 b, respectively. In someembodiments, the conduits may be sized appropriately such that pressuredoes not build up upstream of the oxidizing gas source 106. In suchembodiments, the venturi pump may not be needed.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 400 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 4, the furnace system 400 may include one or more pressuregauges P0, P1, P2, P3, P4, and P5 for monitoring and/or controlling thepressure throughout the furnace system 400. The furnace system 400 mayfurther include one or more thermocouples TC1, TC2, TC3, TC4, and TC5for monitoring and/or controlling the temperature throughout the furnacesystem 400. The furnace system 400 may also include MFC1, a venturi pumpMFC2, and a venturi pump bypass MFC3 to control the flow of variousgases within the furnace system 400. It will be understood that althoughsix pressure gauges, five thermocouples, and three mass flow controllersare depicted in given locations, any suitable number and arrangement ofpressure gauges, thermocouples, and mass flow controllers may beincluded in the furnace system 400.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially, agas inlet pressure may be set at P0 either manually or by the controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The pressure at P1 and P2 should be almostequal. In the context of the current disclosure, about a 0.5 PSIpressure difference in the pressure at P1 and P2 may be considered asalmost equal. P3 should be less than P2 by the leak pressure of thecheck valve 302. The venturi pump MFC2 and the venturi pump bypass MFC3may be utilized to control the back pressure on the venturi pump 402.For example, draw of the effluent gas through the venturi pump 402 maybe controlled via the venturi pump MFC2 and/or venturi pump bypass MFC3,which in turn may control the backpressure on the venturi pump 402. Apressure drop across the venturi pump 402 may be monitored at P4. Insome embodiments, flow through MFC2 may be increased and/or the flowthrough MFC3 may be decreased. In some embodiments, the flow throughMFC2 may be increased and/or the flow through MFC3 may be decreased ifthe pressure drop across the venturi pump 402 is insufficient and fallsbelow a predetermined threshold. In some embodiments, the pressuremeasured at P3 may be slightly above atmospheric pressure, e.g., about30 Hg. In such embodiments, the venturi pump 402 may be configured togenerate vacuums at about 29 Hg. The furnace chamber 102 may be a vacuumfurnace or an atmosphere furnace. In embodiments in which the furnacechamber 102 is an atmosphere furnace, the atmosphere furnace maypotentially use more gas compared to a similar sized vacuum furnace.Accordingly, more dilution gas may be used within the catalyticconverter in the atmosphere furnace than with a vacuum furnace as morevolume exchanges may be generated at vacuum than at atmosphericpressure. In some embodiments, the pressures at P0, P1, P2, P3, P4, andP5 may be monitored by the controller 116 or manually, and processingperformed within the furnace system 400 may be stopped if the pressureat one or more of P0, P1, P2, P3, P4, and P5 exceeds or falls below oneor more predetermined thresholds. In some embodiments, an alarm may beinitiated if the pressure at one or more of P0, P1, P2, P3, P4, and P5exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 400 maybe configured to try to achieve a substantially constant temperature atTC2. That is, the temperature of the catalyst contained in the catalystenclosure 111 a may be maintained at a substantially constanttemperature range. In some embodiments, the temperature at TC2 may bemaintained within a range of 285-600 degrees Celsius. In someembodiments, the temperature at TC2 may depend on the catalyst containedin the catalyst enclosure 111 a. The catalyst heater 111 b may controlthe adjustable setpoint at TC1 based on the monitored temperaturefeedback from TC2. In some embodiments, the adjustable setpoint at TC1may be within a range of 225-425 degrees Celsius. If TC2 is equal to orabove the adjustable setpoint (i.e., if the catalyst gets overheated)the follow steps may be performed: (1) the catalyst heater 111 b may beturned off; (2) the oxidizing gas flow from the oxidizing gas source 106through MFC2 and/or MFC3 may be increased; and/or (3) the inlet gas flowthrough MFC1 may be decreased. In some embodiments, if the CO detector112 detects CO, or detects an amount of CO that meets or exceeds athreshold value, then MFC1, MFC2, and power to the one or more heatingelements 122 may be shut off while MFC3 remains open such thatbackpressure may be provided on the venturi pump 402, the check valve302, and the furnace chamber 102. In some embodiments, an alarm may beinitiated if CO detector 112 detects CO or detects an amount of CO thatmeets or exceeds a threshold value. In some embodiments, one or moreheaters for the furnace exhaust conduit 103 and conduits 406 a-b may becontrolled based on temperatures measured at TC3, TC4, and/or TC5. Insome embodiments, the temperature at TC1, TC2, TC3, TC4, and TC5 may bemonitored by the controller 116 or manually, and processing performedwithin the furnace system 400 may be stopped if the temperature at oneor more of TC1, TC2, TC3, TC4, and TC5 exceeds or falls below one ormore predetermined thresholds. In some embodiments, an alarm may beinitiated if the temperature at one or more of TC1, TC2, TC3, TC4, andTC5 exceeds or falls below one or more predetermined thresholds.

FIG. 5 is a block diagram of a furnace system 500 according to oneembodiment. Similar components shown in FIG. 5 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, 3, and 4. As shown in FIG. 5, thefurnace system 500 may include a binder cracking system 501 and theisolation system 104 may include a check valve 302 and a venturi pump402. The binder cracking system 501 may be positioned downstream fromthe check valve 302 and may include a binder cracking enclosure 502, abinder cracking heater 504, a steam source 505, a flame arrestor 508, avalve 510, and MFC4. The binder cracking enclosure 502 may be fluidlyconnected to the steam source 505 via MFC4. The binder crackingenclosure 502 may also be fluidly connected to the oxidizing gas source106 via the valve 510. In some embodiments, the oxidizing gas source 106may direct oxidizing gas towards the catalytic converter system 110using a vacuum pump and/or the air injector 109, as described inreference to FIG. 1. In some embodiments, one or more of the furnaceexhaust conduit 103, a conduit 506 a between the check valve 302, andthe binder cracking system 501 may be heated in order to prevent orreduce condensation of high molecular weight species in the volatilizedbinder components that may be present in the gaseous effluent.

The binder cracking enclosure 502 may be a heated enclosuresubstantially free of oxygen for decomposing high molecular weightbinder components into lower molecular weight binder components. In thecontext of the current disclosure, the lower molecular weight bindercomponents may typically be gases at room temperature and so arenon-condensable. In some embodiments, the binder cracking enclosure 502may be sized such that the high molecular weight binder components maystay within the binder cracking enclosure 502 a sufficient amount oftime in order to decompose into lower molecular weight bindercomponents. In some embodiments, the binder cracking enclosure 502 maycomprise a catalyst. In such embodiments, the catalyst may lower thetemperature at which the high molecular weight binder componentsdecompose into lower molecular weight binder components. In someembodiments, the binder cracking enclosure 502 may be heated by thebinder cracking heater 504. In some embodiments, the binder crackingheater 504 may comprise an electronic heating component. In someembodiments, the steam source 505 and MFC4 may be used while the bindercracking enclosure 502 is processing volatilized binder components. Insome embodiments, the binder component decomposition may generate someunsatisfied chemical bonds. Such unsatisfied chemical bonds may resultin carbon (C) atoms. In such embodiments, the steam source 505 may beconfigured to provide steam, i.e., H₂0 to the binder cracking enclosure502 such that the steam may react with the carbon to form a combinationof CO and CH₄ and/or a combination of CO and H₂. Accordingly, the steamprovided by the steam source 505 may prevent a carbon deposit within thefurnace system 500, e.g., the binder cracking enclosure 502. In someembodiments, the valve 510 may be configured to provide oxidizing gas tothe binder cracking enclosure 502 to periodically remove carbon buildupfrom the binder cracking enclosure 502. In such embodiments, theoxidizing gas may be provided in between processes, such as sintering,within the furnace system 500. In some embodiments, the binder crackingenclosure 502 may not need the oxidizing gas depending on thecompositions of the volatilized binder components and the inlet gasprovided via the gas inlet conduit 115 to the furnace chamber 102. Forexample, if the inlet gas contains hydrogen, oxidizing gas may not beneeded, as the hydrogen may react with any carbon atoms generated withinthe binder cracking enclosure 502 due to unsatisfied chemical bonds.

The flame arrestor 508 may be configured to prevent the propagation of aflame originating at the binder cracking heater 504 towards thecatalytic converter system 110. Specifically, the flame arrestor 508 mayprevent any flames from propagating due to the heater 504 igniting thegaseous effluent. In some embodiments, the furnace system 500 mayinclude various flame arrestors close to and on either side of any pointof potential ignition for any of the embodiments described herein.Further, although flame arrestor 508 is discussed in conjunction withfurnace system 500, it is contemplated that one or more flame arrestors508 may be incorporated into any furnace system described herein.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 500 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 5, the furnace system 500 may include one or more pressuregauges P0, P1, P2, P3, P4, P5, and P6 for monitoring and/or controllingthe pressure throughout the furnace system 500. The furnace system 500may further include one or more thermocouples TC1, TC2, TC3, TC4, andTC5 for monitoring and/or controlling the temperature throughout thefurnace system 500. The furnace system 500 may also include various massflow controllers MFC1, MFC2, MFC3, and MFC4 to control the flow ofvarious gases within the furnace system 500. It will be understood thatalthough seven pressure gauges, five thermocouples, and four mass flowcontrollers are depicted in given locations, any suitable number andarrangement of pressure gauges, thermocouples, and mass flow controllersmay be included in the furnace system 500.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially, agas inlet pressure may be set at P0 either manually or by the controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The pressure at P2 and the pressure at P1 maybe maintained as approximately equal. In some embodiments, the pressureat P1 and P2 may be maintained as approximately equal. In the context ofthe current disclosure, about a 0.5 PSI pressure difference in thepressure at P1 and P2 may be considered as approximately equal. P3 maybe less than P2 by the leak pressure of the check valve 302. In someembodiments, the leak pressure of the check valve 302 may be about 0.3PSI or larger. There may be a back pressure caused by the bindercracking enclosure 502 as the pressure at P4 may increase depending onthe amount of gas molecules generated within the binder crackingenclosure 502. That is, the pressure within the binder crackingenclosure 502 may increase due to the decomposition of the highmolecular weight binder components. As such, the venturi pump 402 mayprovide relief for the pressure built up at P4. The venturi pump 402 mayrelieve pressure by generating a vacuum on the gaseous effluent inletside of the venturi pump 402 through the use of a flowing gas from theoxidizing gas source 106. In some embodiments, the pressure at P5 may bemonitored and maintained at about atmospheric pressure. Monitoring maybe regular, intermittent, or continuous. By monitoring the pressure atP5 and maintaining it at roughly atmospheric pressure, gas may properlyflow through the furnace system 500. When the pressure at P5 is atroughly atmospheric pressure, this may indicate that gas is properlyflowing. A monitored difference in pressure between P4 and P5 across theflame arrestor 508 should be small. In the context of the currentdisclosure, about a 0.5 PSI pressure differential in the pressure at P4and P5 may be considered small. A relatively large difference inpressure between P4 and P5 may indicate a clog within the flame arrestor508. In some embodiments, the clog may be caused by condensed bindercomponents and/or sooting, which may deposit carbon.

MFC2 and MFC3 may be manipulated to alter furnace system 500. In someembodiments, MFC2 may be used to draw more gaseous effluent through theventuri pump 402, thereby increasing the flow within the furnace system500 and decreasing the pressure at P5. In some embodiments, decreasingthe flow using MFC3 may cause less back pressure on the venturi pump402, thereby decreasing the pressure at P5. In some embodiments, thepressures at P0, P1, P2, P3, P4, P5, and P6 may be monitored by thecontroller 116 or manually, and processing performed within the furnacesystem 500 may be stopped if the pressure at one or more of P0, P1, P2,P3, P4, P5, and P6 exceeds or falls below one or more predeterminedthresholds. In some embodiments, an alarm may be initiated if thepressure at one or more of P0, P1, P2, P3, P4, P5, and P6 exceeds orfalls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 500 maybe configured to try to maintain the temperature at TC2 at asubstantially constant temperature. That is, the temperature of thecatalyst contained in the catalyst enclosure 111 a may be maintained ata substantially constant temperature range. In some embodiments, thetemperature at TC2 may be maintained within a range of 285-600 degreesCelsius. In some embodiments, the temperature at TC2 may depend on thecatalyst contained in the catalyst enclosure 111 a. The catalyst heater111 b may control the adjustable setpoint at TC1 based on the monitoredtemperature feedback from TC2. In some embodiments, the adjustablesetpoint at TC1 may be within a range of 225-425 degrees Celsius. If thetemperature detected at TC2 meets or exceeds the setpoint (i.e., if thecatalyst gets overheated) the following steps may be performed: (1) thecatalyst heater 111 b may be turned off; (2) the oxidizing gas flow fromthe oxidizing gas source 106 through MFC2 or MFC3 may be increased;and/or (3) the inlet gas flow through MFC1 may be decreased. In someembodiments, if the CO detector 112 detects CO, or detects an amount ofCO that meets or exceeds a threshold value, then MFC1, MFC2, MFC4, thebinder cracking heater 504, and the power to the one or more heatingelements 122 may be shut off while MFC3 remains open such thatbackpressure is provided on the venturi pump 402. In some embodiments,an alarm may be initiated. The back pressure provided on the venturipump 402, in turn, may provide back pressure to the check valve 302configured to isolate the furnace chamber 102 from oxidizing gas. Insome embodiments, one or more heaters for the furnace exhaust conduit103 and conduit 506 a may be controlled based on a temperature measuredat TC3. In some embodiments, the temperature at TC1, TC2, TC3, TC4, andTC5 may be monitored by the controller 116 or manually, and processingperformed within the furnace system 500 may be stopped if thetemperature at one or more of TC1, TC2, TC3, TC4, and TC5 exceeds orfalls below one or more predetermined thresholds. In some embodiments,an alarm may be initiated if the temperature at any one of TC1, TC2,TC3, TC4, and TC5 exceeds or falls below one or more predeterminedthresholds.

FIG. 6 is a block diagram of a furnace system 600 according to oneembodiment. Similar components shown in FIG. 6 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, 3, 4, and 5. As shown in FIG. 6, thefurnace system 600 may include a binder trap system 601 and theisolation system may include a check valve 302. The binder trap system601 may itself include a binder trap 602 and a binder trap coolingdevice 604 according to some embodiments. The binder trap 602 may beused to condense or to coalesce volatilized binder components present inthe gaseous effluent, removing at least a portion of the volatilizedbinder components from the gaseous effluent before the gaseous effluentis directed to the catalytic converter system 110. This may reduce theload exerted on the catalytic converter system 110, which may increasethe lifespan of catalytic converter system 110, and/or may reduce thecapacity of catalytic converter system 110 required to create anoffice-safe furnace system 600. In some embodiments, the binder trapsystem 601 may comprise a binder trap bypass conduit fluidly connectedto the furnace exhaust conduit 103 and conduit 603. In such embodiments,gaseous effluent from the furnace chamber 102 may be pumped via one ormore furnace exhaust conduits through the binder trap system 601 or thebinder trap system bypass conduit. In some embodiments, a valve on thebinder trap system bypass conduit may be closed, and the gaseouseffluent may be pumped from the furnace chamber 102 through the bindertrap system 601 during a thermal debinding process. In some embodiments,one or more valves positioned upstream and downstream of the binder trapsystem 601 may be closed, the valve on the binder trap system 601 may beopen, and the gaseous effluent may be pumped from the furnace chamber102 through the binder trap system bypass conduit during a mainsintering (e.g., densification) process.

Binder trap 602 may be a cooled enclosure that traps condensable orcoalescable binder components (i.e., those with a higher boiling point).In some embodiments, the binder trap 602 may include a large interiorsurface area such that the gaseous effluent flowing through the bindertrap 602 impinges on multiple interior surfaces in order for thevolatilized binder components to cool down and condense and/or coalesceout of a gas phase. In some embodiments, the large interior areacomprises a metal insert with a high surface area, e.g., metal meshwool, metal turnings, metal springs, molecular sieve trap, among others.In some embodiments, the metal insert may be a copper insert. In someembodiments, the condensed and/or coalesced binder components may becollected on a surface area of the metal insert during use. In suchembodiments, the metal insert may be detachable, and the metal insertmay be detached to collect and remove the binder components from themetal insert. In some instances, the collected binder components may beremoved using a solvent. In some embodiments, the metal insert may bereattached after removing the binder components. In some embodiments,the binder trap 602 may be cooled by the binder trap cooling device 604to facilitate the condensing or coalescing of volatilized bindercomponents. In such embodiments, heating the portion of the systemdownstream of the binder trap may not be required. In some embodiments,the furnace exhaust conduit 103 may be heated in order to preventcondensation of high molecular weight species in the volatilized bindercomponents present in the gaseous effluent when in the furnace exhaustconduit 103.

In some embodiments, the binder trap 602 may including a cooled surface,e.g., a cooled rod. In some embodiments, the chamber may be acylindrical chamber and the rod may be a coaxial rod removably insertedinto the chamber. In some embodiments, the binder trap cooling device604 may be configured to cool the coaxial rod and/or the cylindricalchamber. In some embodiments, the coaxial rod comprise a tube containingliquid nitrogen to cool the coaxial rod. The cylindrical chamber maycomprise an inlet on a first end of the cylindrical chamber and anoutlet on an opposing second end of the cylindrical chamber.Accordingly, the gaseous effluent directed into the inlet of thecylindrical chamber may flow along the length of the coaxial rod withinthe cylindrical chamber towards the outlet of the cylindrical chamber.The volatilized binder components present in the gaseous effluent maycondense and/or coalesce when the volatilized binder components contactsa surface of the coaxial rod and/or the cylindrical chamber.Accordingly, the condensed and/or coalesced binder components may becollected on one or more surfaces of the coaxial rod and/or thecylindrical chamber. In some embodiments, the coaxial rod and/or thecylindrical chamber may be detached and the collected binder componentsmay be removed. In some instances, the collected binder components maybe removed using a solvent. In some embodiments, the coaxial rod and/orthe cylindrical chamber may be reattached after the collected bindercomponents have been removed. For example, in some embodiments, the rodmay be a tube, e.g., an elongated tube with approximately a 1-inchdiameter, containing liquid nitrogen or another suitable coolant. Inother embodiments, a cooled molecular sieve trap may be used to condenseand/or coalesce binder components. Once binder components have beencollected, the molecular sieve trap may be thrown out or regenerated byheating under vacuum. In still other embodiments, a cooling trap may beformed by producing one or more tortuous cooled flow paths. For example,a cooled chamber containing copper mesh may be used to condense and/orcoalesce binder components. Such an embodiment may operate similarly toa molecular sieve.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 600 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 6, the furnace system 600 may include one or more pressuregauges P0, P1, P2, P3, P4, P5, and P6 for monitoring and/or controllingthe pressure throughout the furnace system 600. The furnace system 600may also include one or more thermocouples TC1, TC2, TC3, and TC4 formonitoring and/or controlling the temperature throughout the furnacesystem 600. The furnace system 600 may further include various mass flowcontrollers MFC1 and MFC2 to control the flow of various gases withinthe furnace system 600. In some embodiments, the oxidizing gas source106 may direct oxidizing gas towards the catalytic converter system 110using a vacuum pump and/or the air injector 109, as described inreference to FIG. 1. It will be understood that although seven pressuregauges, four thermocouples, and two mass flow controllers are depictedin given locations, any suitable number and arrangement of pressuregauges, thermocouples, and mass flow controllers may be included in thefurnace system 600.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially, agas inlet pressure may be set at P0 either manually or by controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The pressure at P2 and P1 may be almost equal.In the context of the current disclosure, about a 0.5 PSI pressuredifference in the pressure at P1 and P2 may be considered as almostequal. P3 may be less than P2 by the leak pressure of the check valve302. The pressure control within furnace system 600 may be primarilycontrolled via MFC2 and MFC1. The conduits may be sized appropriately sothat there is no significant pressure buildup as oxidizing gas from MFC2is mixed with effluent. If the pressure at P2, P3 or P4 is over apredetermined safety threshold, then the flows through MFC2 and/or MFC1may be decreased. In some embodiments, the flow through MFC2 may bedecreased first and then the flow through MFC1 may be decreased. In someembodiments, the pressures at P0, P1, P2, P3, P4, P5, and P6 may bemonitored by the controller 116 or manually, and processing performedwithin the furnace system 600 may be stopped if the pressure at one ormore of P0, P1, P2, P3, P4, P5, and P6 exceeds or falls below one ormore predetermined thresholds. In some embodiments, an alarm may beinitiated if the pressure at one or more of P0, P1, P2, P3, P4, P5, andP6 exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 600 maybe configured to try to achieve a substantially constant temperature atTC2. That is, the temperature of the catalyst contained in the catalystenclosure 111 a may be maintained at a substantially constanttemperature range. In some embodiments, the temperature at TC2 may bemaintained within a range of 285-600 degrees Celsius. In someembodiments, the temperature at TC2 may depend on the catalyst containedin the catalyst enclosure 111 a. The catalyst heater 111 b mayeffectively control the adjustable setpoint at TC1 based on themonitored temperature from TC2. In some embodiments, the adjustablesetpoint at TC1 may be within a range of 225-425 degrees Celsius. If atemperature measured by TC2 meets or exceeds the setpoint (i.e., if thecatalyst gets overheated) the following steps may be performed: (1) thecatalyst heater 111 b may be turned off; (2) the oxidizing gas flow fromthe oxidizing gas source 106 through MFC2 may be increased; and/or (3)the inlet gas flow through MFC1 may be decreased. In some embodiments,if the CO detector 112 detects CO, or detects an amount of CO that meetsor exceeds a threshold value, then MFC land power to the one or moreheating elements 122 may be shut off while MFC2 and/or MFC3 may remainopen such that back pressure is provided on the check valve 302 and thefurnace chamber 102. In some embodiments, an alarm may be initiated ifCO detector 112 detects CO or detects an amount of CO that meets orexceeds a threshold value.

The binder trap 602 may be cooled during a sintering process within thefurnace system 600. The binder trap cooling device 604 may be configuredto cool the binder trap 602 based on the temperature at TC4. In someembodiments, the binder trap cooling device 604 may utilize fluidcooling (e.g., water and/or air cooling), one or more fans, acombination of a thermoelectric cooler and one or more fans, or a heatpipe, among others, to control the temperature of the binder trap 602.In some embodiments, one or more heaters for the furnace exhaust conduit103 may be controlled based on a temperature measured at TC3. In someembodiments, the temperature at TC1, TC2, TC3, and TC4 may be monitoredby the controller 116 or manually, and processing performed within thefurnace system 600 may be stopped if the temperature at one or more ofTC1, TC2, TC3, and TC4 exceeds or falls below one or more predeterminedthresholds. In some embodiments, an alarm may be initiated if thetemperature at one or more of TC1, TC2, TC3, and TC4 exceeds or fallsbelow one or more predetermined thresholds.

FIG. 7 is a block diagram of a furnace system 700 according to oneembodiment. Similar components shown in FIG. 7 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, 3, 4, 5, and 6. As shown in FIG. 7, theisolation system 104 may include a proportional valve 702. The furnacesystem 700 may include the binder trap system 601 as described abovewith respect to FIG. 6. Although the binder trap system 601 is depictedin FIG. 7, it is also contemplated that furnace system 700 may notinclude binder trap system 601 and may only include proportional valve702.

The proportional valve 702 may function to isolate the furnace chamber102 from the oxidizing gas source 106 (e.g., a blower or compressedair). In some embodiments, the proportional valve 702 may comprise aproportional butterfly valve and/or a proportional solenoid valve. Thefurnace system 700 may include a pressure gauge P2 disposed between thefurnace chamber 102 and the proportional valve 702. In some embodiments,the controller 116 may be communicatively connected to the pressuregauge P2 and the proportional valve 702. As such, the controller 116 maybe configured to adjust a position of the proportional valve 702 tomaintain a desired pressure drop across the proportional valve 702. Thefurnace exhaust conduit 103 may be heated in order to prevent or reducecondensation of high molecular weight species in the volatilized bindercomponents present in the gaseous effluent. MFC1 may adjustably controlthe gas inlet such that a sufficient quantity of non-reactive gas ispresent in the gaseous effluent. In some embodiments, a sufficientquantity of non-reactive gas may indicate a proportion of non-reactivegas present in the gaseous effluent great enough to bring the gaseouseffluent below a lower explosive limit (LEL). The mixture of thenon-reactive gas, the volatilized binder effluent, and the oxidizing gasmay not form an explosive or self igniting mixture before entering thecatalytic converter system 110.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 700 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 7, the furnace system 700 may include one or more pressuregauges P0, P1, P2, P3, and P4 for monitoring and/or controlling thepressure throughout the furnace system 700. The furnace system 700 mayalso include one or more thermocouples TC1, TC2, TC3 and TC4 formonitoring and/or controlling the temperature throughout the furnacesystem 700. The furnace system 700 may further include various mass flowcontrollers MFC1 and MFC2 to control the flow of various gases withinthe furnace system 700. In some embodiments, the oxidizing gas source106 may direct oxidizing gas towards the catalytic converter system 110using a vacuum pump and/or the air injector 109, as described inreference to FIG. 1. It will be understood that although five pressuregauges, four thermocouples, and two mass flow controllers are depictedin given locations, any suitable number and arrangement of pressuregauges, thermocouples, and mass flow controllers may be included in thefurnace system 700.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially,gas inlet pressure may be set at P0. In some embodiments, the gas inletpressure at P0 may be set in a range of 0-10 PSI. For example, the gasinlet pressure at P0 may be set in a range of 0-3 PSI when the furnacechamber 102 comprises a ceramic tube furnace chamber. As anotherexample, the gas inlet pressure at P0 may be set in a range of 0-10 PSIwhen the furnace chamber 102 comprises a metal furnace chamber. Thepressure at P2 may be monitored, and the pressure at P2 and P1 should bemaintained to be almost equal. In the context of the current disclosure,about a 0.5 PSI pressure difference in the pressure at P1 and P2 may beconsidered as almost equal. The proportional valve 702 may control thedifference in pressure between P3 and P4. A pressure difference may beset so that the back flow of gas is decreased or minimized. In someembodiments, the pressure difference between P3 and P4 may be set toabout a 3 PSI difference, where the pressure at P3 is higher than thatthe pressure at P4. In some embodiments, the pressures at P0, P1, P2,P3, and P4 may be monitored by the controller 116 or manually, andprocessing performed within the furnace system 700 may be stopped if thepressure at one or more of P0, P1, P2, P3, and P4 exceeds or falls belowone or more predetermined thresholds. In some embodiments, an alarm maybe initiated if the pressure at one or more of P0, P1, P2, P3, and P4exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 700 maybe configured to try to maintain the temperature at TC2 at asubstantially constant temperature. That is, the temperature of thecatalyst contained in the catalyst enclosure 111 a may be maintained ata substantially constant temperature range. In some embodiments, thetemperature at TC2 may be maintained within a range of 285-600 degreesCelsius. In some embodiments, the temperature at TC2 may depend on thecatalyst contained in the catalyst enclosure 111 a. The catalyst heater111 b may control the adjustable setpoint at TC1 based on the monitoredtemperature feedback from TC2. In some embodiments, the adjustablesetpoint at TC1 may be within a range of 225-425 degrees Celsius. If thetemperature at TC2 meets and/or exceeds the setpoint (i.e., if thecatalyst gets overheated) the following steps may be performed: (1) thecatalyst heater 111 b may be turned off; (2) the oxidizing gas flow fromthe oxidizing gas source 106 through MFC2 may be increased; and (3) theinlet gas flow through MFC1 may be decreased. The CO detector 112detects CO from flowing out of the catalytic converter system 110. Insome embodiments, if the CO detector 112 detects CO, or detects anamount of CO that meets or exceeds a threshold value, then MFC1, MFC2,and power to the one or more heating elements 122 may be are shut offand/or an alarm may be initiated. In some embodiments, one or moreheaters for the furnace exhaust conduit 103 may be controlled based on atemperature measured at TC3. In some embodiments, the temperature atTC1, TC2, TC3, and TC4 may be monitored by the controller 116 ormanually, and processing performed within the furnace system 700 may bestopped if the temperature at one or more of TC1, TC2, TC3, and TC4exceeds or falls below one or more predetermined thresholds. In someembodiments, an alarm may be initiated if the temperature at one or moreof TC1, TC2, TC3, and TC4 exceeds or falls below one or morepredetermined thresholds.

FIG. 8 is a block diagram of a furnace system 800 according to oneembodiment. Similar components shown in FIG. 8 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, 3, 4, 5, 6, and 7. As shown in FIG. 8,the isolation system 104 may include a pump 802. The furnace system 800may also include the binder trap system 601, which may function asdescribed above with reference to FIG. 6. Although the binder trapsystem 601 is depicted in FIG. 8, it is also contemplated that furnacesystem 800 may not include binder trap system 601 and may only includepump 802.

The pump 802 may function to isolate the furnace chamber 102 from theoxidizing gas source 106 (e.g., a blower or compressed air). In someembodiments, the pump 802 may be a low speed pump, e.g., a variable lowspeed pump. In such embodiments, the low speed pump may draw a smallamount such that the pump 802 may keep up with the flow of the gaseouseffluent within the furnace chamber 800 and may not generate a vacuum.For example, the flow through the pump 802 may be equal to the flowthrough MFC 1. In some embodiments, the pump 802 may be a positivedisplacement pump, a lobe pump, a diaphragm pump, a peristaltic pump,and/or a piston pump. In some embodiments, the pump 802 may be avariable speed low speed pump. In such embodiments, the pump 802 may becontrolled based on a pressure measurement at P3. The pump 802 maymaintain a pressure difference across the pump 802 and may prevent backdiffusion of oxidizing gas into the furnace chamber 102. In someembodiments, the furnace system 800 may include a conduit 804 fluidlyconnecting the pump 802 and the catalytic converter system 110. In someembodiments, the pump 802 may prevent back diffusion of bindercomponents into the catalytic converter system 110. The furnace exhaustconduit 103 may be heated in order to prevent condensation of highmolecular weight species in the volatilized binder components present inthe gaseous effluent. MFC1 may adjustably control the gas inlet suchthat a sufficient quantity of non-reactive gas is present in the gaseouseffluent. In some embodiments, a sufficient quantity of non-reactive gasmay indicate a proportion of the non-reactive gas present in the gaseouseffluent that is large enough to bring the gaseous effluent below alower explosive limit (LEL). The mixture of the non-reactive gas, thevolatilized binder effluent, and the oxidizing gas may not form anexplosive or self igniting mixture before entering the catalyticconverter system 110.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 800 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 8, the furnace system 800 may include one or more pressuregauges P0, P1, P2, P3, and P4 for monitoring and/or controlling thepressure throughout the furnace system 800. The furnace system 800 mayalso include one or more thermocouples TC1, TC2, TC3, and TC4 formonitoring and/or controlling the temperature throughout the furnacesystem 800. The furnace system 800 may further include various mass flowcontrollers MFC1 and MFC2 to control the flow of various gases withinthe furnace system 800. It will be understood that although fivepressure gauges, four thermocouples, and two mass flow controllers aredepicted in given locations, any suitable number and arrangement ofpressure gauges, thermocouples, and mass flow controllers may beincluded in the furnace system 800. In some embodiments, the oxidizinggas source 106 may direct oxidizing gas towards the catalytic convertersystem 110 using the vacuum pump 107 and/or the air injector 109, asdescribed in reference to FIG. 1.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially,gas inlet pressure may be set at P0 either manually or by controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The pressures at P2 and P3 may be monitored,and the pressure at P2 may be maintained as about the same pressure asthe pressure at P1. In the context of the current disclosure, about a0.5 PSI pressure difference in the pressure at P1 and P2 may beconsidered as about the same pressure. The pump 802 may maintain asubstantially constant pressure range across P3 and P4. In someembodiments, the pump 802 may be a variable low speed pump. In suchembodiments, the pump 802 may be controlled based on at least themeasured pressure at P3. In some embodiments, the pressures at P0, P1,P2, P3, and P4 may be monitored by the controller 116 or manually, andprocessing performed within the furnace system 800 may be stopped if thepressure at one or more of P0, P1, P2, P3, and P4 exceeds or falls belowone or more predetermined thresholds. In some embodiments, an alarm maybe initiated if the pressure at one or more of P0, P1, P2, P3, and P4exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 800 maybe configured to try to maintain the temperature at TC2 at asubstantially constant temperature. That is, the temperature of thecatalyst contained in the catalyst enclosure 111 a may be maintained ata substantially constant temperature range. In some embodiments, thetemperature at TC2 may be maintained within a range of 285-600 degreesCelsius. In some embodiments, the temperature at TC2 may depend on thecatalyst contained in the catalyst enclosure 111 a. The catalyst heater111 b controls the adjustable setpoint at TC1 based on the monitoredtemperature feedback from TC2. In some embodiments, the adjustablesetpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2meets or exceeds the setpoint (i.e., if the catalyst gets overheated)the following steps may be performed: (1) the catalyst heater 111 b maybe turned off; (2) the oxidizing gas flow from the oxidizing gas source106 through MFC2 may be increased; and (3) the inlet gas flow throughMFC1 may be decreased. In some embodiments, the speed of pump 802 mayslow down to match the decreased flow of the inlet gas flow throughMFC1. Eventually the inlet gas flow through MFC1 may be stopped, therebyisolating the furnace chamber 102 from the oxidizing gas source 106. Insome embodiments, if the CO detector 112 detects CO, or detects anamount of CO that meets or exceeds a threshold value, then MFC1, MFC2,and power to the one or more heating elements 122 may be shut off. Insome embodiments, the temperature at TC1, TC2, TC3, and TC4 may bemonitored by the controller 116 or manually, and processing performedwithin the furnace system 800 may be stopped if the temperature at oneor more of TC1, TC2, TC3, and TC4 exceeds or falls below one or morepredetermined thresholds. In some embodiments, an alarm may be initiatedif the temperature at one or more of TC1, TC2, TC3, and TC4 exceeds orfalls below one or more predetermined thresholds.

FIGS. 9A-B are block diagrams of variations of a furnace system 900according to exemplary embodiments. As shown in FIG. 9A, the isolationsystem 104 may include an extended exhaust conduit 902 a. In someembodiments, the extended exhaust conduit 902 a may be an extension ofthe furnace exhaust conduit 103. The extended exhaust conduit 902 aisolates the furnace chamber 102 from the oxidizing gas source 106(e.g., a blower or compressor). As shown in FIG. 9A, the extendedexhaust conduit 902 a may be a conduit of sufficient length andtortuosity such that back diffusion of oxidizing gas against a flow ofgaseous effluent exiting the furnace chamber 102 is reduced orminimized. Extended exhaust conduit 902 a may have, e.g., serpentine,zig-zag, corkscrew, or other tortuous shapes having regular or irregularundulations.

As shown in FIG. 9B, the extended exhaust conduit 902 b may be a conduitof sufficient length and dimension with minimal tortuosity or linearshape, according to some embodiments. In such embodiments, the extendedexhaust conduit 902 b may be an extension of the furnace exhaust conduit103. The extended exhaust conduit 902 b may be of sufficient dimension(e.g., length and cross section) such that the back diffusion ofoxidizing gas against the flow of gaseous effluent exiting the furnacechamber 102 may be reduced or minimized. For example, the extendedexhaust conduit 902 b may reduce the back diffusion of oxidizing gasagainst a flow of gaseous effluent exiting the furnace chamber 102 suchthat the oxidizing gas concentration in the furnace chamber 102 may beless than a predetermined threshold, e.g., 1 parts per billion (ppb) or1 parts per million (ppm). The predetermined threshold for the oxidizingconcentration may depend on a material of the part 126 being processedin the furnace chamber 102. For example, the predetermined threshold maybe about 1 ppb when the part 126 is composed of titanium, which may beslightly lower than the predetermined threshold when the part 126 iscomposed of steel. In such embodiments, a gas flow may be 0.001 litersper minute to several standard liters per minute (slm). In someembodiments, the gas flow may depend on a size of the furnace chamber102. For example, the gas flow in the furnace chamber 102 of anindustrial furnace may be about 20-50 slm. Exemplary embodiments of theextended exhaust conduit 902 b with sufficient dimensions (e.g., lengthand cross section) for reduced back diffusion are described in furtherdetail below.

The extended exhaust conduit 902 b may have dimensions (e.g., length andcross section) designed to facilitate gas flow at a given rate and toprovide a Peclet number sufficiently high in magnitude, with the flow ofappropriate direction, for limiting concentration of a certain gas,e.g., oxidizing gas, to a predetermined amount, e.g., less than 1 ppb or1 ppm, within the furnace chamber 102. In some embodiments, the Pecletnumber may be of magnitude greater than one of 10, 20, 40, 100, and1000. That is, for a given flow of effluent gas, the dimensions of theextended exhaust conduit 902 b may be selected so as to provide a Pecletnumber sufficiently high in magnitude, with the flow of appropriatedirection, to maintain the furnace chamber 102 at less than or equal to1 ppb or 1 ppm.

As a non-limiting first example, when nitrogen is used as a process gasin the furnace chamber 102 and the catalytic converter system 110operates at 500 degrees Celsius, the extended exhaust conduit 902 b maycomprise a length of 50 mm and an inside diameter of 1.7 mm tofacilitate a process gas flow of about 0.0017 slm and reduce or minimizethe back diffusion of oxidizing gas against a flow of gaseous effluentsuch that the oxidizing gas concentration in the furnace chamber 102 isabout 1 ppb. That is, the extended exhaust conduit 902 b may beconfigured to reduce or minimize the back diffusion of oxidizing gas to1 ppb when the process gas flow is about 0.0017 slm. In someembodiments, the furnace chamber 102 fluidly connected to the extendedexhaust conduit 902 b configured to maintain a predetermined oxidizinggas concentration, e.g., about 1 ppb, may include an oxidizing gasconcentration larger than the predetermined oxidizing gas concentration,e.g., about 1 ppm. This may be due to leaks within the furnace system900 and/or unwanted process gas within the furnace chamber 102.Accordingly, the furnace chamber 102 may under perform compared to theisolation system 104, i.e., the extended exhaust conduit 902 b. That is,the large oxidizing gas concentration in the furnace chamber 102 may becontributed more to such leaks and/or unwanted process gas compared tothe reduced back diffusion of oxidizing gas from the isolation system104. In some embodiments, the back diffusion of oxidizing gas used inthe catalytic converter system 110 may be maintained at a level that maybe orders of magnitude below other sources of oxidizing gas, such asleaks, virtual leaks, and unwanted process gas. For example, the backdiffusion of the oxidizing gas used in the catalytic converter system110 may be maintained at about 1 ppb where the oxidizing gasconcentration in the furnace chamber 102 may be about 10 ppm (or 10,000ppb). In this example, the back diffusion of the oxidizing gas used inthe catalytic converter system 110 may be about 4 orders of magnitudebelow other sources of oxidizing gas for the furnace chamber 102. It isunderstood that one order of magnitude indicates a factor of 10.

An exemplary Matlab script providing exemplary calculations fordetermining the dimensions of the extended exhaust conduit 902 b isprovided below with related description following the Matlab script. Asshown below, several comments are embedded in the Matlab script toprovide context and clarity.

% Example calculation for back-diffusion prevention in a tube (e.g.,extended exhaust conduit 902 b)%1D model, L>>dia (as shown in FIGS. 9B-9Cdia=(0.125-0.03*2)*25.4/1000;% [m] internal diameter of the tubeL=0.05;% [m] length of the tube% C0=200e3;% [ppm] concentration of impurity species in ‘dirty’ region:e.g., O₂ in atmosphereC0=781e3; % [ppm] concentration of impurity species in ‘dirty’ region:e.g., N₂ in atmosphereC1=1e-3;% [ppm] target concentration of impurity species in ‘clean’chamberTgas=700;% [K] temperature of the gas at which to evaluate thediffusivity and fluid properties% Operate at atmospheric pressurerho=0.69528; %[kg/m{circumflex over ( )}3] density of the gas at theprescribed temperaturemew=4.3492e-5; % [Pa*s] kinematic viscosity of the gas at the prescribedtemperature% Calculations followPe=−1*log(C1/C0);% [-] required Peclet number to achieve concentrationslisted aboveA=dia{circumflex over ( )}2*pi/4; % [m{circumflex over ( )}2]cross-sectional area of the tube% Calculate the diffusivity of the two species of interest, e.g., O₂ andN₂kb=1.380649e-23;% [J/K] Botlzmann constantAv=6.022140858e23; % [g/mol] Avagadro's number% Assume pressure differential between chamber (e.g., furnace chamber102) and ambient issmall, and impact on diffusivity % and density is also small. Thisassumption is checked later.ma=40/Av/1000; %[kg] atomic mass of species A: argonmb=28/Av/1000; %[kg] atomic mass of species B: N₂% mb=32/Av/1000; %[kg] atomic mass of species B: O₂da=1.94e-10; %[m] diameter of species A: argondb=1.5e-10; %[m] diameter of species B: N₂% db=1.46e-10; %[m] diameter of species B: O₂P=14.696/0.000145038; % [Pa] estimate of absolute gas pressure (1 atm)in the chamber (e.g., furnace chamber 102) and in the approximationthroughout the tube (e.g., extended exhaust conduit 902 b) (see commentabove assuming now pressure drop)D=⅔*sqrt(kb{circumflex over ( )}3/pi{circumflex over( )}3)*sqrt(1/(2*ma)+1/(2*mb))*4*Tgas{circumflex over ( )}(3/2)/(P*(da+db){circumflex over ( )}2); %[-] Binary diffusioncoefficient of the two speciesu=Pe*D/L; %[m/s] % required mean flow velocity in the tubeQ=u*A; % [m{circumflex over ( )}3/s] % required volumetric flow rate inthe tube, at TgasRe=rho*u*dia/mew; % [-] Reynolds number, for checking laminar assumption<2300delP=128*L/pi*mew*Q/dia{circumflex over ( )}4*0.000145038;% [psi]pressure drop in circular tube from viscous flow% If pressure delta is not small as compared to absolute pressure,re-evaluate properties

For the calculations provided in the Matlab script, the furnace chamber102 may maintain a specified impurity concentration, e.g., an atmospheresubstantially free of oxygen, against regular atmosphere using theextended exhaust conduit 902 b. Oxidizing gas may be an important gas toprevent from flowing back into the furnace chamber 102. In someembodiments, the extended exhaust conduit 902 b may be configured toprevent back diffusion of nitrogen, which may have a slightly higherdiffusion coefficient in a clean gas compared to oxidizing gas, and/orwater vapor, i.e., gaseous H20. In the context of the currentdisclosure, the diffusion coefficient (D) may indicate a proportionalitycoefficient between the flux of species and the gradient of species. Thediffusion coefficient may have a unit of (length)²/time. For example, ahigher diffusion coefficient for flux (J), where J=−D·dc/dz, indicates ahigher flux (J) for a same gradient (dc/dz). For the calculations above,the furnace chamber 102 may use nitrogen as a processing gas, and theextended exhaust conduit 902 b may be configured to prevent oxidizinggas back diffusion.

As described with reference to the non-limiting first example, theextended exhaust conduit 902 b may have a length of approximately 50 mmand an inner diameter of approximately 1.7 mm to facilitate a nitrogenprocessing gas mass flow of approximately 0.0017 slm. The extendedexhaust conduit 902 b may be configured to maintain an oxidizing gasconcentration of 1 ppb in the furnace chamber 102. In some embodiments,the atmospheric oxidizing gas concentration may be 200,000 ppm, and thebinary diffusion coefficient between the nitrogen processing gas and theoxidizing gas may be estimated to be 8.76e-5 m²/s at a mean gastemperature of 700K and 1 atmospheric pressure. In some embodiments, thebinary diffusion coefficient between the nitrogen processing gas and theoxidizing gas may be derived using the Chapman-Enskog theory, asexplained in pages 123-124 of “The Properties of Gases and Liquids,” theentirety of which is incorporated by reference into this application.See REID, R. C., PRAUSNITZ, J. M., & POLING, B. E. (1987). Theproperties of gases and liquids. New York, McGraw-Hill. In someembodiments, the magnitude of the Peclet number and the direction of gasflow needed to maintain oxidizing gas concentration of 1 ppb in thefurnace chamber 102 may be approximately 19.11.

Given the above dimensions of the extended exhaust conduit 902 b, themean gas velocity in the extended exhaust conduit 902 b may be 34 mm/s.In some embodiments, the mean gas velocity may be converted to a volumeflow rate based on a cross-sectional area of the extended exhaustconduit 902 b. The volume flow rate may then be converted to a mass flowrate of approximately 0.0017 slm, where density temperature dependency(e.g., PV=nRT) of the flowing gas (e.g., the nitrogen processing gas)may be considered in this conversion to the mass flow rate. In someembodiments, the pressure drop across the extended exhaust conduit 902 bmay be negligibly small.

For the purpose of the calculation with respect to the Matlab script,the following assumptions may apply: (1) an optimal gas mixing in thefurnace chamber 102; (2) the nitrogen gas directed into the furnacechamber 102 is clean, which indicates that there are no additionalsources of impurity species other than the oxidizing gas, therebyallowing an observation of the efficiency of the extended exhaustconduit 902 b in reducing or minimizing back diffusion of oxidizing gas;(3) the furnace system 900 is isothermal (i.e., uniform temperaturethroughout the entire furnace system 900) and in a steady state (i.e.,properties measured at each and any point in the furnace system 900 maynot vary in time); (4) tracks one contaminant species, i.e., theoxidizing gas; and (5) the length of the extended exhaust conduit 902 bis large with respect to its diameter.

In some embodiments, the extended exhaust conduit 902 b may scale in gasconsumption for more stringent purity requirements (i.e., loweroxidizing gas concentration requirements). For example, the mass flowrate of the nitrogen gas may be increased from 0.0017 slm to 0.0019 slm(about an 11% increase in the amount of gas) in order to reduce anoxidizing gas concentration of 1 ppb to 0.1 ppb. Accordingly, areduction in the oxidizing gas concentration of about an order ofmagnitude may be achieved by flowing about 11% more nitrogen gas.

It is understood that the calculations included in the Matlab scriptrefer to the non-limiting first example only, and variations of thecalculations included in the Matlab script may be performed inalternative embodiments. It is also understood that the varioussimplifying assumptions with reference to the calculations included inthe Matlab script have been made solely for the purpose of explanationand clarity. As such, it is understood that variations of thecalculations included in the Matlab script may be provided withreference to alternative embodiments of the furnace system.

Another method of calculation for extended exhaust conduit 902 bdimensions is explained in further detail as follows with reference toFIGS. 9C-9F. As shown in FIG. 9C, the furnace chamber 102 may operate atan atmospheric pressure. The furnace chamber 102, which may include aheated reservoir, may receive an uncontaminated processing gas(hereinafter referred to as clean processing gas), e.g., nitrogen,through the gas inlet 115, and gaseous effluent may be directed out ofthe furnace chamber 102 through the extended exhaust conduit 902 b andtowards the catalytic converter system 110. The clean processing gas maybe flowed through the gas inlet 115 into the furnace chamber 102 at afirst rate of mass flow, where the clean processing gas has a firstconcentration of a species of molecules comprising the first rate ofmass flow. The gaseous effluent may flow out of the furnace chamber 102at a second rate of mass flow, where the gaseous effluent has a secondconcentration of the species of molecules comprising the second rate ofmass flow. The material present in the furnace chamber 102 may be in awell-mixed state. That is, a measurement of material exiting the furnacechamber 102 may be an appropriate approximation of the actualcomposition of the material present in the furnace chamber 102, assumingthe samples are taken at approximately the same time. In someembodiments, the clean processing gas and the gaseous effluent may notbe isothermal. In some embodiments, the clean processing gas and thegaseous effluent may be isothermal. In some embodiments, the cleanprocessing gas and the gaseous effluent may not maintain a sametemperature in the furnace system 900. For example, the clean processinggas may be at a temperature between approximately 20 and approximately50 degrees Celsius and the gaseous effluent may be at a temperaturebetween approximately 300 and approximately 1,400 degrees Celsius. Insome embodiments, an air injector 109 (also referred to as an oxygeninjector, which may introduce air or oxygen gas into the extendedexhaust conduit 902 b) may be coupled to the extended exhaust conduit902 b downstream of the furnace chamber 102. In some embodiments, theair injector 109 may be positioned upstream of the catalytic convertersystem 110.

The extended exhaust conduit 902 b may be configured to prevent backdiffusion of oxidizing gas towards the furnace chamber 102. The furnacechamber 102 may need to be maintained at an atmosphere substantiallyfree of oxygen. In some embodiments, an atmosphere substantially free ofoxygen may be considered as an atmosphere including an oxidizing gasconcentration of approximately 10 ppm or less.

For the purpose of this method of calculation, the following assumptionsmay apply: (1) a continuum transport (i.e., not a transition transportor a molecular transport); (2) model as isothermal (i.e., uniformtemperature throughout the furnace system 900) and at steady state(i.e., the furnace system 900 is in a steady state)); (3) model as a onedimensional transport, where L>>d (i.e., changes along the length of theextended exhaust conduit 902 b may be of more significance than that ofthe inner diameter); (4) an sufficient gas mixing in the furnace chamber102; and (5) tracks one contaminant species, e.g., the oxidizing gas.For the purpose of this method of calculation, a temperature differencemay help. For example, transport may be encouraged from a relatively hotchamber to a relatively colder chamber (e.g., a chamber or part of achamber containing impurities), where migration may occur from hot tocold (also referred to as thermophoresis).

As shown in FIG. 9C, c₁ indicates a concentration of a contaminantspecies in the furnace chamber 102, c₀ indicates a concentration of thecontaminant species at the distal end of the extended exhaust conduit902 b (i.e., the end of the extended exhaust conduit 902 b distal to thefurnace chamber 102), d indicates an inside diameter of the extendedexhaust conduit 902 b, L indicates a length of the extended exhaustconduit 902 b, and u indicates a mean velocity of the gaseous effluentgas flow in the extended exhaust conduit 902 b. In some embodiments, theconcentration of the contaminant species in the extended exhaust conduit902 b may be based on the amount of back diffusion of the contaminantspecies. In some embodiments, the concentration of the contaminantspecies in the extended exhaust conduit 902 b may be further based onthe concentration of the contaminant species in the gaseous effluent. Insome embodiments, the contaminant species may be the oxidizing gas. Insome embodiments, the mean velocity u may encompass the inner diameter dand a prescribed volumetric rate of gas flow per time. In someembodiments, d may be negligibly small compared to L. Given the abovenoted assumptions, the following equation may be obtained based on therelationship between c₁, c₀, d, and u:

$\begin{matrix}{{\frac{\partial c}{\partial t} + {u\frac{\partial c}{\partial z}}} = {D\frac{\partial^{2}c}{\partial z^{2}}}} & (1)\end{matrix}$

where t indicates time, c indicates a concentration profile of thecontaminant species, D indicates a diffusivity of the contaminantspecies, and z indicates a position along the extended exhaust conduit902 b. As there is no time dependency due to the assumption that thiscalculation is considering a steady state,

$\frac{\partial c}{\partial t}$

equals 0. Accordingly, the equation (1) may become:

$\begin{matrix}{{u\frac{\partial c}{\partial z}} = {D\frac{\partial^{2}c}{\partial z^{2}}}} & (2)\end{matrix}$

In some embodiments, an ordinary differential equation of equation (2)with scaled, or normalized, variables may be derived as follows:

$\begin{matrix}{{{Pe}\frac{d\hat{c}}{d\hat{z}}} = \frac{d^{2}\hat{c}}{d{\hat{z}}^{2}}} & (3)\end{matrix}$

where the length z may be scaled with the total length of the extendedexhaust conduit 902 b as

${\hat{z} = \frac{z}{L}},$

the concentration of the contaminant species throughout the furnacesystem 900 may be scaled with the concentration of the contaminantspecies at the distal end of the extended exhaust conduit 902 b as

${\hat{c} = \frac{c}{c_{0}}},{{{and}\mspace{14mu} {Pe}} = {\frac{uL}{D}.}}$

In some embodiments, ĉ and {circumflex over (z)} are transformations toa dimensionless space. That is, dimensionless equation (3) may bederived from equation (2), which is in a dimensional form. In someembodiments, a first boundary constraint may be provided as ĉ=1 at{circumflex over (z)}=0 and a second boundary constraint may be providedas ĉ=0 at {circumflex over (z)}=1. In some embodiments, {circumflex over(z)} indicates a normalized position along the extended exhaust conduit902 b, and ĉ indicates a normalized concentration profile of thecontaminant species.

In some embodiments, the following equation may be derived from equation(3):

$\begin{matrix}{{c(z)} = \frac{{c_{0}( {e^{Pe} - e^{\frac{z}{l} \cdot {Pe}}} )} + {c_{1}( {e^{\frac{z}{l} \cdot {Pe}} - 1} )}}{( {e^{Pe} - 1} )}} & {(4)\text{-}1}\end{matrix}$

In some embodiments, equation (4)-1, which is in a dimensional form, maybe normalized by dividing equation (4)-1 with c₀, thereby obtainingdimensionless equation as follows:

$\begin{matrix}{\hat{c} = \frac{e^{Pe} - e^{\hat{z}{Pe}} + {\frac{c_{1}}{c_{0}}( {e^{\hat{z}{Pe}} - 1} )}}{e^{Pe} - 1}} & {(4)\text{-}2}\end{matrix}$

where ĉ is plotted as shown in FIG. 9D according to some embodiments. Asshown in FIG. 9D, the ĉ, i.e., normalized concentration profiles, may beplotted as a function of a normalized position ({circumflex over (z)})and Peclet number (Pe) 922, 924, 926, 928, and 930. As shown in FIG. 9D,{circumflex over (z)}=0 indicates a position furthest away from thefurnace chamber 102 on the extended exhaust conduit 902 b (the distalend of the extended exhaust conduit 902 b), and {circumflex over (z)}=1indicates a position adjacent to the furnace chamber 102 on the extendedexhaust conduit 902 b (the proximal end of the extended exhaust conduit902 b). This indicates that the gas flow within the extended exhaustconduit 902 b flows from z=L towards z=0 (FIG. 9C). Accordingly, a meanvelocity (u) and the Peclet number may be less than zero. Theconcentration of the contaminant species may be highest when {circumflexover (z)} is approximately 0, and the concentration of the contaminantspecies may be approximately 0 when {circumflex over (z)} isapproximately 1. As shown in FIG. 9D, the concentration profile of thecontaminant species may be largest toward smaller values of the position{circumflex over (z)}. Further, the concentration species may becomehigher as {circumflex over (z)} becomes smaller along the extendedexhaust conduit. In contrast, the concentration profile of thecontaminant species may become lower as {circumflex over (z)} getshigher. Further, FIG. 9D shows that an extended exhaust conduit 902 bproviding a lower (e.g., more negative) Pe number may better preventback diffusion of the contaminant species towards the furnace chamber102.

In some embodiments, a flux (J) (i.e., the rate (per time) at which thecontaminant species pass through an area) is derived based on equation(4)-2 as follows:

$\begin{matrix}{\mspace{76mu} {J = {{{- D}\frac{dc}{dz}} = {\frac{{- D}\frac{Pe}{L}}{e^{Pe} - 1}( {{{- c_{0}}e^{\frac{z}{L} \cdot {Pe}}} + {c_{1}e^{\frac{z}{L} \cdot {Pe}}}} )}}}} & {(5)\text{-}1} \\{\mspace{76mu} {J = {{\frac{{- D}{\frac{Pe}{L} \cdot c_{0}}}{e^{Pe} - 1}( {{- e^{\frac{z}{L} \cdot {Pe}}} + {\frac{c_{1}}{c_{0}}e^{\frac{z}{L} \cdot {Pe}}}} )\mspace{14mu} {where}\mspace{14mu} {Pe}} = \frac{\overset{\_}{u} \cdot L}{D}}}} & {(5)\text{-}2} \\{\mspace{76mu} {J = {\frac{{- \overset{\_}{u}} \cdot c_{0}}{e^{Pe} - 1}( {{- 1} + \frac{c_{1}}{c_{0}}} )e^{\frac{z}{L} \cdot {Pe}}}}} & {(5)\text{-}3} \\{J = {\frac{\overset{\_}{u} \cdot c_{0}}{e^{Pe} - 1}( {1 - \frac{c_{1}}{c_{0}}} )e^{\frac{z}{L} \cdot {Pe}}\mspace{14mu} {where}\mspace{14mu} {flux}\mspace{14mu} {may}\mspace{14mu} {be}\mspace{14mu} {referred}\mspace{14mu} {to}\mspace{14mu} {in}\mspace{14mu} {units}\mspace{14mu} {of}\mspace{14mu} ( {{amount}\mspace{14mu} {of}\mspace{14mu} {species}} )\text{/}{m^{2} \cdot s}}} & {(5)\text{-}4}\end{matrix}$

In some embodiments, a normalized flux (Ĵ) may be derived as follows:

$\begin{matrix}{\hat{J} = {\frac{J}{( \frac{{Dc}_{0}}{L} )} = {\frac{{- {Pe}}\mspace{14mu} e^{\hat{z}{Pe}}}{e^{Pe} - 1}( {\frac{c_{1}}{c_{0}} - 1} )}}} & (6)\end{matrix}$

FIG. 9E illustrates an exemplary embodiment of the normalized flux (Ĵ)as a function of the Peclet number, where the magnitude of the Pecletnumber is small.

Referring back to FIG. 9C, a steady-state value is now calculated. Asdescribed above, it may be assumed that clean processing gas may bedirected into the furnace chamber 102. It may be further assumed that:(1) the concentration values are dimensional; (2) Pe may be positive ornegative, where a negative Pe indicates a gas flow away from the furnacechamber 102 and a positive Pe indicates a gas flow towards the furnacechamber 102; (3) a ratio of concentration profiles may be utilized todetermine ppm; and (4) the atmospheric oxidizing gas concentration maybe approximately 200,000 ppm by volume.

In some embodiments, the rate of change in contaminant speciesconcentration profile may be provided by the following equation:

{Rate of change of species in the chamber}={(Species passing into thefurnace chamber 102)−(Species passing out of the furnace chamber102)}  (7)

In some embodiments, the rate of change of species in the chamber may beset as zero. That is, the concentration of the contaminant specieswithin the furnace chamber 102 may be considered at a steady state.Further, the concentration of contaminant species flowing from thefurnace chamber 102 to the exhaust conduit 902 b may balance theconcentration of the back diffused contaminant species present in theextended exhaust conduit 902 b In such embodiments, equation (7) may beprovided as follows:

0={flux in}−{flux out}  (8)-1

Equation (8)-1 may be rearranged such that the flux (J) derived above inequation (5) or (6) multiplied by the area (i.e., the cross sectionalarea of the extended exhaust conduit 902 b as defined by inner diameterd) may equal a concentration profile of the contaminant speciesmultiplied by a velocity of gas flow and further multiplied by the area,as shown in the following equation:

$\begin{matrix}{0 = {\{ {{Flux}*{Area}} \} - \{ {( {{Concentration}\mspace{14mu} {in}\mspace{14mu} {chamber}} )*{Velocity}*{Area}} \}}} & {(8)\text{-}2} \\{\mspace{76mu} {= {\{ {A\frac{\overset{\_}{u} \cdot c_{0}}{e^{Pe} - 1}( {\frac{c_{1}}{c_{0}} - 1} )e^{\frac{z}{L} \cdot {Pe}}} \} - \{ {\overset{\_}{u} \cdot A \cdot c_{1}} \}}}} & {(8)\text{-}3}\end{matrix}$

In some embodiments, equation (8)-3 may be rearranged as follows:

$\begin{matrix}{{\frac{c_{0}}{( {e^{Pe} - 1} )}( {\frac{c_{1}}{c_{0}} - 1} )e^{Pe}} = c_{1}} & {(9)\text{-}1} \\{{c_{0}( {\frac{c_{1}}{c_{0}} - 1} )} = {c_{1}\frac{( {e^{Pe} - 1} )}{e^{Pe}}}} & {(9)\text{-}2} \\{{{c_{0}c_{1}} - c_{0}} = {c_{1}\frac{( {e^{Pe} - 1} )}{e^{Pe}}}} & {(9)\text{-}3} \\{{c_{1}( {1 - \frac{( {e^{Pe} - 1} )}{e^{Pe}}} )} = c_{0}} & {(9)\text{-}4}\end{matrix}$

Accordingly, the concentration within the furnace chamber 102 (c₁), theconcentration at the distal end of the extended exhaust conduit 902 b(c₀), and the Peclet number (Pe) may be shown to relate based onequation (8) as follows

$\begin{matrix}{c_{1} = \frac{c_{0}}{( {1 - \frac{( {e^{Pe} - 1} )}{e^{Pe}}} )}} & (10)\end{matrix}$

where equation (10) is a rearrangement of equation (9)-4. As shown inequation (10), the concentration of the contaminant species (c₁) may beprovided in terms of the c₀, and the Pe. In some embodiments,

${Pe} = {\frac{uL}{D}.}$

The ratio of species

$\frac{c_{1}}{c_{0}}$

may be plotted as shown in FIG. 9F according to some embodiments.Accordingly, the concentration of the contaminant species (c₁) may beprovided in terms of the c₀, extended exhaust conduit 902 b (e.g.,length (L) and inside diameter (d)), and the diffusivity of thecontaminant species (D), as shown in the following equation:

$\begin{matrix}{c_{1} = \frac{c_{0}}{1 - \frac{e^{\frac{uL}{D}} - 1}{e^{\frac{uL}{D}}}}} & (11)\end{matrix}$

Air is comprised of about 20.9% oxygen by volume, which is about 209,000ppm/vol. Accordingly, to achieve a concentration of 10 ppb/vol withinthe furnace chamber 102, the ratio of

$\frac{c_{1}}{c_{0}}$

may be 4.7×10⁻⁸. Accordingly, a target quotient of contaminant specieswithin the furnace chamber 102 as compared to the distal end of theextended exhaust conduit 902 b may be estimated as 1×10⁻⁹ and themagnitude of Pe may be derived as 20 based on equations (10) and (11).

Referring back to FIG. 9C, the concentration of the contaminant species(c₁) may be further derived based on an exit volume flow rate of thegaseous effluent (Q_(out)). As a first step, an inlet volume flow rateof the clean processing gas may be determined. In some embodiments, theinlet volume flow rate may be set with an MFC. In a second step, an exitvolume flow rate of the gaseous effluent (Q_(out)) may be derived basedon the inlet volume flow rate of the clean processing gas and a changein temperature between the clean processing gas and the gaseouseffluent. In some embodiments, the second step may be computed asQ_(out)=T_(out)/T_(in)*Q_(in), where Q_(in) indicates the inlet flowrate, T_(out) indicates a temperature of the gaseous effluent, andT_(in) indicates a temperature of the clean processing gas. In a thirdstep, the mean velocity (u) may be derived based on the exit volume flowrate and the area (A) of the extended exhaust conduit 902 b. In suchembodiments, u may be the equivalent of Q_(out)/A. In a fourth step, areasonable diffusivity (D) of the contaminant species may be obtained,as explained in “The Properties of Gases and Liquids” at pages 123-124.In some embodiments, the diffusivity (D) of the contaminant species mayincrease with temperature. The obtained diffusivity of the contaminantspecies may be a diffusivity value corresponding to a relatively hightemperature above room temperature. In some embodiments, the diffusivityvalue corresponding to the relatively high temperature may be selectedbecause the contaminant species may be more mobile at highertemperatures, which may increase a possibility of the contaminantspecies contaminating the furnace chamber 102 (i.e., increase thepossibility of back diffusion of the contaminant species). In someembodiments, the diffusivity (D) of the contaminant species may beadjusted using the Champman-Enskog result (T{circumflex over ( )}3/2) oran empirical correlation (T{circumflex over ( )}1.75) based on thefollowing equation:

$\begin{matrix}{\frac{D\; 1}{D\; 2} = ( \frac{T\; 1}{T\; 2} )^{x}} & (12)\end{matrix}$

where x indicates a predetermined exponent, and 1 or 2 (e.g., D1 and T1or D2 and T2) may each correspond to one of the reference and/oradjusted states in absolute temperature. Table 1 below providesnon-limiting examples of the diffusivity (D) of oxygen when the cleanprocessing gas is air, Ar, and N₂, where the temperature indicates thetemperature at which the diffusivity may be measured or computed

TABLE 1 Pair Temp, K D, cm∧2/s Air-O2 273 0.176  Ar-O2 300 0.454 N2-O2293.2 0.22

In a fifth step, the concentration of the contaminant species (c₁) maybe determined using equation (11) based on the extended exhaust conduit902 b dimensions (e.g., length L and inside diameter d), the derivedmean velocity (u), and the determined diffusivity (D) of the contaminantspecies.

As another non-limiting example, when nitrogen is used as a process gasin the furnace chamber 102 and the catalytic converter system 110operates at 500 degrees Celsius, the extended exhaust conduit 902 b maycomprise a length of 20 cm and an inside diameter of about 6 mm tofacilitate a gaseous effluent gas flow of 1 slm and reduce or minimizethe back diffusion of oxidizing gas against the flow of gaseous effluentsuch that the gas concentration in the furnace chamber 102 due to backdiffusion is below 1 ppm or below 1 ppb. That is, the extended exhaustconduit 902 b may be configured to reduce or minimize the back diffusionof oxidizing gas to below 1 ppm or below 1 ppb when the gaseous effluentis flowing through the extended exhaust conduit 902 b at a relativelyhigh gas flow of 1 slm. In some embodiments, the extended exhaustconduit 902 b may comprise a relatively large inside diameter forpractical reasons, such as avoidance of clogging, e.g., caused by bindercomponents. In such embodiments, the extended exhaust conduit 902 b maybe lengthened in accordance to the larger inside diameter. For example,the length of the extended exhaust conduit 902 b may be increased byapproximately the square of the increase in the inside diameter of theextended exhaust conduit 902 b (hereinafter referred to as “square lawscaling relationship”). In some embodiments, a similar isolationperformance, i.e., prevention of oxidizing gas back diffusion, may beobtained as long as the square law scaling relationship is observed. Insome embodiments, the square law scaling relationship may apply to arange of particle flow (pf) parameters spanning laminar flow and/orturbulent flow, as opposed to molecular or transition flow within thefurnace system 900. In some embodiments, the square law scalingrelationship may apply in vacuum pressures within the furnace system900.

It is understood that the examples provided above are non-limiting, andthe dimensions for the extended exhaust conduit 902 b may vary dependingon the furnace system 900, e.g., for any gaseous effluent gas flow andfurnace chamber 102 impurity requirement, such that the extended exhaustconduit 902 b achieves a Peclet number sufficiently high in magnitude,with the fib of appropriate direction, for the gaseous effluent gas flowto reduce or minimize back diffusion of oxidizing gas.

As shown in FIGS. 9A-B, the extended exhaust conduit 902 a-b is fluidlyconnected to a conduit 906, which may be a separate conduit or acontinuation of extended exhaust conduit 902 a-b via a valve V1. One orand both of extended exhaust conduit 902 a-b and conduit 906 may beheated in order to prevent condensation of high molecular weight speciesin the volatilized binder components present in the gaseous effluent.MFC1 may adjustably control the gas inlet such that a sufficientquantity of non-reactive gas is present in the gaseous effluent. In someembodiments, a sufficient quantity of non-reactive gas may indicate aproportion of the non-reactive gas present in the gaseous effluent largeenough to bring the gaseous effluent below a lower explosive limit(LEL). The mixture of the non-reactive gas, the volatilized bindereffluent, and the oxidizing gas do not form an explosive or selfigniting mixture before entering the catalytic converter system 110. Insome embodiments, the furnace system 900 may further include a bindersystem 601 disposed between the furnace chamber 102 and MFC2.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 900 shown in FIGS. 9A-9B isdescribed below. In some embodiments, the controller 116 may control theexemplary process for pressure control and catalyst temperature controlas follows. As shown in FIGS. 9A-9B, the furnace system 900 may includeone or more pressure gauges P0, P1, P2, and P3 for monitoring and/orcontrolling the pressure throughout the furnace system 900. The furnacesystem 900 may further include one or more thermocouples TC1, TC2, andTC3 for monitoring and/or controlling the temperature throughout thefurnace system 900. The furnace system 900 may also include various massflow controllers MFC1 and MFC2 to control the flow of various gaseswithin the furnace system 900. It will be understood that although fourpressure gauges, three thermocouples, and two mass flow controllers aredepicted in given locations, any suitable number and arrangement ofpressure gauges, thermocouples, and mass flow controllers may beincluded in the furnace system 900.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially,gas inlet pressure may be set at P0. In some embodiments, the gas inletpressure at P0 may be set in a range of 0-10 PSI. For example, the gasinlet pressure at P0 may be set in a range of 0-3 PSI when the furnacechamber 102 comprises a ceramic tube furnace chamber. As anotherexample, the gas inlet pressure at P0 may be set in a range of 0-10 PSIwhen the furnace chamber 102 comprises a metal furnace chamber. Thepressures at P2 and P3 may be monitored, and the monitored pressures atP2 and P3 may be maintained as about the same pressure as the pressureat P0. In the context of the current disclosure, a pressure differenceof about 0.5 PSI may be considered as about the same pressure. Thecontrol of pressure for the furnace system 900 may be focused on theinitial pressure setting at P0 and the flow of oxidizing gas from theoxidizing gas source 106 via MFC2. That is, the pressure control withinfurnace system 900 may be primarily controlled via MFC2 and the initialpressure setting at P0. In some embodiments, the pressures at P0, P1,P2, and P3 may be monitored by the controller 116 or manually, andprocessing performed within the furnace system 900 may be stopped if thepressure at one or more of P0, P1, P2, and P3 exceeds or falls below oneor more predetermined thresholds. In some embodiments, an alarm may beinitiated if the pressure at one or more of P0, P1, P2, and P3 exceedsor falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 900 maybe configured to try to maintain the temperature at TC2 at asubstantially constant temperature. That is, the temperature of thecatalyst contained in the catalyst enclosure 111 a may be maintained ata substantially constant temperature range. In some embodiments, thetemperature at TC2 may be maintained within a range of 285-600 degreesCelsius. In some embodiments, the temperature at TC2 may depend on thecatalyst contained in the catalyst enclosure 111 a. The catalyst heater111 b may effectively control the adjustable setpoint at TC1 based onthe monitored temperature from TC2. In some embodiments, the adjustablesetpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2meets or exceeds the setpoint (i.e., if the catalyst gets overheated)the following steps may be performed: (1) the catalyst heater 111 b maybe turned off; (2) the oxidizing gas flow from the oxidizing gas source106 through MFC2 may be increased; (3) the inlet gas flow through MFC1may be decreased; and/or (4) valve V1 may be closed. The CO detector 112detects CO from flowing out of the catalytic converter system 110. Insome embodiments, if the CO detector 112 detects CO, or detects anamount of CO that meets or exceeds a threshold value, then MFC1, MFC2,and power to the one or more heating elements 122 may be shut off and/oran alarm may be triggered. In some embodiments, one or more heaters forthe extended exhaust conduit 902 a-b and/or conduit 906 may becontrolled based on a temperature measured by TC3. In some embodiments,the furnace system 900 may include multiple TCs configured to monitorand/or control the one or more heaters for the extended exhaust conduit902 a-b and the conduit 906. In some embodiments, the temperature atTC1, TC2, and TC3 may be monitored by the controller 116 or manually,and processing performed within the furnace system 900 may be stopped ifthe temperature at one or more of TC1, TC2, and TC3 exceeds or fallsbelow one or more predetermined thresholds. In some embodiments, analarm may be initiated if the temperature at one or more of TC1, TC2,and TC3 exceeds or falls below one or more predetermined thresholds.

FIG. 10 is a block diagram of a furnace system 1000 according to oneembodiment. Similar components shown in FIG. 10 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, 3, 4, 5, 6, 7, 8, and 9. As shown inFIG. 10, the isolation system 104 may include a porous plug 1002 and aplug heater 1004. The porous plug 1002 may isolate the furnace chamber102 from the oxidizing gas source 106 (e.g., a blower or compressedair). In some embodiments, the porous plug 1002 may be a micro porousplug. The porous plug 1002 may function to maintain a pressuredifference across the porous plug 1002, and the small pores of porousplug 1002 may prevent back diffusion of oxidizing gas into the furnacechamber 102. In some embodiments, the size of the pores in the porousplug 1002 may be designed such that the pores are significantly largerthan the mean free path of gas molecules, e.g., oxidizing gas. Suchpores, of sizes significantly larger than the mean free path (mfp) ofgas molecules, may allow the gas molecules to move around relative toeach other to interact with each other. That is, when the mfp of gasmolecules is relatively larger than the pore size, the gas molecules mayinteract with the walls of the pores and not each other. Accordingly,the forward flow of the gaseous effluent may not effectively preventback diffusion of oxidizing gas. Instead, prevention of back diffusionof oxidizing gas into the furnace chamber 102 may depend on a pressuredifference between the furnace chamber 102 and the catalytic convertersystem 110. In some embodiments, the furnace exhaust conduit 103 may bea conduit of sufficient length and tortuosity such that back diffusionof oxidizing gas against a flow of gaseous effluent exiting the furnacechamber 102 is reduced or minimized. For example, a sufficienttortuosity of the furnace exhaust conduit 103 may increase the velocityof the gaseous effluent such that a ratio of convective transport todiffusive transport is increased.

In some embodiments, the porous plug 1002 may be configured tofacilitate the gaseous effluent flow and provide a Peclet numbersufficiently high in magnitude, with the flow of appropriate direction,for limiting concentration of a certain gas, e.g., oxidizing gas, to apredetermined amount in an upstream direction, e.g., less than 1 ppb or1 ppm, as described above with reference to the extended exhaust conduit902 b and related figures. In some embodiments, the porous plug 1002 maybe considered as an approximate equivalent of the extended exhaustconduit 902 b at least to the extent that any passive isolationarrangement for any give gas flow may be considered to have an effectivePeclet number. For example, the porous plug 1002, e.g., a porousgraphite plug, may include a plurality of parallel conduits, each ofwhich comprise a certain dimension, e.g., length and inside diameter.Each of the plurality of parallel conduits may provide a Peclet number,as described above with reference to the extended exhaust conduit 902 b.In some instances, each length of the multiple parallel conduits throughporous plug 1002 may be summed to obtain a total length, and each insidediameter may be summed to obtain a total inside diameter. The totallength and the total inside diameter may be the equivalent of the lengthand the inside diameter of the extended exhaust conduit 902 b of FIG. 9Bconfigured to provide a certain Peclet number. Accordingly, the porousplug 1002 may provide an equivalent Peclet number, thereby reducing orminimizing the back diffusion of oxidizing gas at a similar rate as theequivalent extended exhaust conduit 902 b. As such, the exemplarycalculations and considerations described above with reference to theextended exhaust conduit 902 b of FIG. 9B may apply to the porous plug1002. In some embodiments, the porous plug 1002 may be configured toconstrain the gaseous effluent flow such that the gas flow velocity iselevated, thereby reducing or minimizing the back diffusion of oxidizinggas. For example, the porous plug 1002 may include pores larger thanabout 1 micron, which may be sufficient to facilitate molecular flow ofthe gaseous effluent at atmospheric pressure.

As shown in FIG. 10, the furnace system 1000 may include the furnaceexhaust conduit 103 fluidly connecting the furnace chamber 102 and theporous plug 1002, a conduit 1006 a fluidly connected to a conduit 1006 bvia a valve V1 where the conduits 1006 a-b fluidly connect the porousplug 1002 to the catalytic converter system 100. The valve V1 may beleft open during a sintering processing in the furnace system 1000. Insome embodiments, the furnace system 1000 may include a plug heater 1004configured to heat the porous plug 1002. The furnace exhaust conduit103, conduits 1006 a-b and/or the porous plug 1002 may be heated inorder to prevent condensation of high molecular weight species in thevolatilized binder components present in the gaseous effluent. MFC1 mayadjustably control the gas inlet such that a sufficient quantity ofnon-reactive gas is present in the gaseous effluent. In someembodiments, a sufficient quantity of non-reactive gas may indicate aproportion of the non-reactive gas present in the gaseous effluent largeenough to bring the gaseous effluent below a lower explosive limit(LEL). The mixture of the non-reactive gas, the volatilized bindereffluent, and the oxidizing gas may not form an explosive or selfigniting mixture before entering the catalytic converter system 110. Insome embodiments, the furnace system 1000 may include a binder trapsystem (not shown in FIG. 10) disposed between the furnace chamber 102and the porous plug 1002. The binder trap system may be used to condenseor to coalesce volatilized binder components present in the gaseouseffluent removing at least a portion of the volatilized bindercomponents from the gaseous effluent before the gaseous effluent isdirected to the catalytic converter system 110.

An exemplary process for pressure control and catalyst temperaturecontrol with reference to the furnace system 1000 is described below. Insome embodiments, the controller 116 may control the exemplary processfor pressure control and catalyst temperature control as follows. Asshown in FIG. 10, the furnace system 1000 may include one or morepressure gauges P0, P1, P2, and P3 for monitoring and/or controlling thepressure throughout the furnace system 1000. The furnace system 1000 mayfurther include one or more thermocouples TC1, TC2, TC3, and TC4 formonitoring and/or controlling the temperature throughout the furnacesystem 1000. The furnace system 1000 may also include various mass flowcontrollers MFC1 and MFC2 to control the flow of various gases withinthe furnace system 1000. It will be understood that although fourpressure gauges, four thermocouples, and two mass flow controllers aredepicted in given locations, any suitable number and arrangement ofpressure gauges, thermocouples, and mass flow controllers may beincluded in the furnace system 1000. In some embodiments, an oxidizinggas source 106 may direct oxidizing gas towards the catalytic convertersystem 110 using a vacuum pump and/or the air injector 109, as describedin reference to FIG. 1.

With respect to pressure control, pressure may be controlled so as tonot over-pressurize the furnace chamber 102 so as to not compromise thecomponents connected downstream of the furnace chamber 102. Initially,gas inlet pressure may be set at P0 either manually or by the controller116. In some embodiments, the gas inlet pressure at P0 may be set in arange of 0-10 PSI. For example, the gas inlet pressure at P0 may be setin a range of 0-3 PSI when the furnace chamber 102 comprises a ceramictube furnace chamber. As another example, the gas inlet pressure at P0may be set in a range of 0-10 PSI when the furnace chamber 102 comprisesa metal furnace chamber. The pressures at P2 and P3 may be monitored,and the pressures at P1 and P2 may be maintained at about the samepressure. In the context of the current disclosure, about a 0.5 PSIpressure difference in the pressure at P1 and P2 may be considered asabout the same pressure. The pressure at P3 may be relatively lower thanP1 and P2 due to a pressure drop across the porous plug 1002 and theintroduction of oxidizing gas from the oxidizing gas source 106 via MFC2into conduit 1006 b. The control of pressure for the furnace system 1000may be focused on the initial pressure setting at P1 and the flow ofoxidizing gas from the oxidizing gas source 106 via MFC2. Accordingly,in the event of overpressure within the furnace system 1000, the inletgas conduit 115 may be closed. In some embodiments, the overpressure maybe caused by clogged binder components in the porous plug 1002. In suchembodiments, providing additional heat to the porous plug 1002 via theplug heater 1004 may dislodge clogged binder components, permittinginlet gas conduit 115 to be re-opened and permitting continued operationof furnace system 1000. In some embodiments, the pressures at P0, P1,P2, and P3 may be monitored by the controller 116 or manually, andprocessing performed within the furnace system 1000 may be stopped ifthe pressure at one or more of P0, P1, P2, and P3 exceeds or falls belowone or more predetermined thresholds. In some embodiments, an alarm maybe initiated if the pressure at one or more of P0, P1, P2, and P3exceeds or falls below one or more predetermined thresholds.

With respect to catalyst temperature control, the furnace system 800 maybe configured to try to maintain the temperature at TC2 at asubstantially constant temperature. That is, the temperature of thecatalyst contained in the catalyst enclosure 111 a may be maintained ata substantially constant temperature range. In some embodiments, thetemperature at TC2 may be maintained within a range of 285-600 degreesCelsius. In some embodiments, the temperature at TC2 may depend on thecatalyst contained in the catalyst enclosure 111 a. The catalyst heater111 b may control the adjustable setpoint at TC1 based on the monitoredtemperature feedback from TC2. In some embodiments, the adjustablesetpoint at TC1 may be within a range of 225-425 degrees Celsius. If TC2meets or exceeds the setpoint (i.e., if the catalyst gets overheated)the following steps may be performed: (1) the catalyst heater 111 b maybe turned off; (2) the oxidizing gas flow from the oxidizing gas source106 through MFC2 may be increased; (3) the inlet gas flow through MFC1may be decreased; and/or (4) valve V1 may be closed. The CO detector 112may detect CO flowing out of the catalytic converter system 110. In someembodiments, an alarm may be initiated if CO detector 112 detects CO ordetects an amount of CO that meets or exceeds a threshold value. MFC1,MFC2, and power to the one or more heating elements 122 may be shut offupon CO detection. In some embodiments, the temperature at TC1, TC2,TC3, and TC4 may be monitored by the controller 116 or manually, andprocessing performed within the furnace system 1000 may be stopped ifthe temperature at one or more of TC1, TC2, TC3, and TC4 exceeds orfalls below one or more predetermined thresholds. In some embodiments,an alarm may be initiated if the temperature at one or more of TC1, TC2,TC3, and TC4 exceeds or falls below one or more predeterminedthresholds.

FIG. 11 depicts a block diagram of a furnace system 1100 according toone embodiment. Similar components shown in FIG. 11 may operate in asubstantially similar manner as the corresponding components describedin reference to FIGS. 1, 2A-2B, 3, 4, 5, 6, 7, 8, 9, and 10. As shown inFIG. 11, the furnace system 1100 is an embodiment of the furnace system100 comprising a binder trap system 601, as described above withreference to FIG. 6. The isolation system 104 included in the furnacesystem 1100 comprises a vacuum pump 1107, as described with reference toFIG. 1. As shown in FIG. 11, the furnace system 1100 comprises ademister 1108, as described with reference to FIG. 1. In someembodiments, the furnace system 1100 further comprises a binder trapsystem bypass conduit 1105. In some embodiments, the vacuum pump 1107may pump the gaseous effluent from the furnace chamber 102 via one ormore furnace exhaust conduits through the binder trap system 601 or thebinder trap system bypass conduit 1105. In some embodiments, a valve 101on the binder trap system bypass conduit 1105 may be closed, and thegaseous effluent may be pumped from the furnace chamber 102 through thebinder trap system 601 during a thermal debinding process of the part126. In such embodiments, the gaseous effluent may include volatilizedbinder components, which may be passed through the binder trap system601 and directed to the catalytic converter system 110. In someembodiments, one or more valves positioned upstream and/or downstream ofthe binder trap system 601 may be closed, valve 101 may be open, and thegaseous effluent may be pumped from the furnace chamber 102 through thebinder trap system bypass conduit 1105 during a main sintering (e.g.,densification) process of the part 126. In such embodiments, the gaseouseffluent may bypass the binder trap system 601 and may be directed tothe catalytic converter system 110. As described above, the gaseouseffluent may be directed to bypass or pass through the binder trapsystem 601 depending on the type of processing for the part 126. Forexample, the gaseous effluent may be directed to pass through the bindertrap system 601 during a thermal debinding process when volatized bindercomponent is being generated and the catalytic converter system 110 isbeing used to remove the volatized binder component from the effluent.As another example, the gaseous effluent may be directed to bypass thebinder trap system 601 during a main sintering process (e.g.,densification) when less or no volatized binder component is beingproduced.

As shown in FIG. 11, the furnace system 1100 may include one or morepressure regulated gas sources, which may each include a process gassupply, a pressure regulator, and one or more pressure gauges and/orvalves, e.g., P3, P4, and V3. Valve V3 may be a gas cylinder isolationvalve V3 (a second gas cylinder isolation valve V4 is not shown in FIG.11). The furnace system 1100 may also include a chamber isolation valveV7, an annulus valve V8 (also referred to as valve 101 with reference toFIG. 1), main vacuum valve V9, a vacuum vent valve V11, and an inletisolation valve V100.

The furnace system 1100 may further include a control thermocouple TC1,a retort thermocouple TC4 for monitoring the load in the furnace chamber102, a vacuum line heater thermocouple TC8, a binder trap thermocoupleTC10; a vacuum pump overtemp thermocouple TC12; a catalyst temperaturethermocouple TC13; and a catalyst exhaust thermocouple TC14. In someembodiments, the furnace system 1100 may further include a furnacechamber 102 over temperature thermocouple (not shown in FIG. 11, butpotentially included). It will be understood that any suitable numberand arrangement of thermocouples and valves be included in the furnacesystem 1100.

The furnace system 1100 may also include a chamber pressure/vacuumsensor P2, a gas high pressure/vacuum sensor P3 (a second a gas highpressure/vacuum sensor P5 is not shown in FIG. 11 but may be included),a gas low pressure/vacuum sensor P4 (a second gas low pressure/vacuumsensor P6 is not shown in FIG. 11), pump fore line pressure/vacuumsensor P7, and a furnace chamber positive pressure sensor P9. It will beunderstood that any suitable number and arrangement of pressure/vacuumsensors (also referred to as pressure gauges) be included in the furnacesystem 1100.

The furnace system 1100 may also include a heater H₂ to heat the furnaceexhaust conduit 103 and/or the binder trap 602, and a catalyst heater H3(also referred to as catalyst heater 111 b in FIG. 1) configured to theheat the catalytic converter system 110. In some embodiments, the bindertrap cooler 604 may include a thermoelectric cooler (TEC), e.g., apeltier cooling device, or a TEC fan.

Described below is an exemplary procedure with reference to the furnacesystem 1100 according to one embodiment. In some embodiments, theexemplary procedure described below may be applied to a vacuum furnacesystem where the pressure may be substantially below atmosphericpressure. For example, the pressure may be below 10 Torr, where 1atmospheric pressure is 760 Torr. While the procedure explained below isdescribed with reference to a sintering process performed in the furnacesystem 1100, this is not required and the furnace system 1100 may beutilized for various types of processing in alternative embodiments.

In the context of the current disclosure, the following terms are usedto described the catalyst temperature monitored and controlled by TC14:(1) T0 is a temperature below which the setpoint of the catalyst heaterH3 is about equal to T10 (T10 will be described in further detail belowwith respect to the terms with reference to TC13); (2) T1 is atemperature at which the setpoint of the catalyst heater H3 is loweredat TC13; (3) T2 is a minimum temperature at which catalyst oxidizesvolatilized binder components; (4) T3 is a temperature at which thesetpoint of the catalyst heater H3 at TC13 is about equal to T11 (H3power may be under closed loop control between T1 and T3; T11 will bedescribed in further detail below with respect to the terms withreference to TC13); (5) T4 is a temperature at which a ramp rate of afurnace program (falling temperature) will resume/continue; (6) T5 is atemperature at which a ramp rate of the furnace program (risingtemperature) will pause; (7) T6 is a temperature at which V7 will closedue to rising temperature; and (8) T7 is a maximum safe operatingtemperature of the catalyst. The furnace program may be configured toabort if the temperature at TC14 exceeds T7. In some embodiments, T0 maybe about 225 degrees Celsius; T1 may be about 270 degrees Celsius; T2may be about 280 degrees Celsius; T3 may be about 315 degrees Celsius;T4 may be about 365 degrees Celsius; T5 may be about 475 degreesCelsius; T6 may be about 525 degrees Celsius; and T7 may be about 575degrees Celsius. The temperatures listed above are approximatetemperatures, and it is understood that the temperature values may varydepending on a type of catalyst and/or binder used in the furnace system1100, among other factors, in alternative embodiments.

In the context of the current disclosure, the following terms are usedto describe the catalyst heater temperature monitored and controlled byTC13: (1) T8 is a maximum temperature at which a processing within thefurnace system 1100 is configured to abort if a monitored temperature atTC13 exceeds T8; (2) T10 is a maximum setpoint of the catalyst heater H3at TC13; and (3) T11 is a minimum setpoint of the catalyst heater H3 atTC13. In some embodiments, the catalyst heater H3 setpoint may be variedbetween temperature T1 and T3 above at TC14. In some embodiments, T8 maybe 600 degrees Celsius; T10 may be 400 degrees Celsius; and T11 may be275 degrees Celsius. The temperatures listed above are approximatetemperatures, and it is understood that the temperature values may varydepending on a type of catalyst and/or binder used in the furnace system1100, among other factors, in alternative embodiments.

In some embodiments, the relative values of the temperatures listedabove may be as follows: T0<T1<T2<T3<T4<T5<T6<T7, where T8 is similarto, but not equal to, T7, and T11<T10. That is, the setpoint of thecatalyst heater H3 is low when the temperature at TC14 is high and thesetpoint of catalyst heater H3 is high when the temperature at TC14 islow.

In the context of the current disclosure, the following terms are usedto described a furnace pressure at P2: (1) PV1 is a pressure at whichthe ramp rate of the furnace program will resume (e.g., PV1 indicatesfalling pressure within the furnace chamber 102); and (2) PV2 is apressure at which the ramp rate of the furnace program will pause (e.g.,PV1 indicates rising pressure within the furnace chamber 102), wherePV1<PV2. In some embodiments, the furnace pressure at P2 may be at abaseline pressure of 1-2 Torr. In such embodiments, PV2 may be around5-6 Torr, and PV1 may be around 3-4 Torr. In some embodiments, thefurnace pressure at P2 may be lower, e.g., 0.1-1 Torr. In suchembodiments, PV2 may be around 4-5 Torr and PV1 may be around 2-3 Torr.The pressures listed above are approximate pressures, and it isunderstood that the pressure values may vary in alternative embodiments.

Referring back to FIG. 11, an exemplary procedure with reference to asintering process in the furnace system 1100 is described in detailbelow. In some embodiments, the exemplary procedure may be a controlmethod performed by the controller 116.

At the beginning of the sintering process, the furnace chamber 102 maybe loaded with a part 126 for a sintering process and closed. As notedabove, the sintering process in the context of the current disclosuremay include at least one of a thermal debinding process and a mainsintering process (e.g., densification). Subsequently, V3 may be closedand MFC 113 may be set to zero flow. The vacuum pump 107 may be turnedon and may remain operational for the duration of the procedure. Afterthe vacuum pump 107 is started: (1) V7 and V9 may be opened, and (2) V8may be closed. In some embodiments, V7 may be fluidly connected viainternal conduits to the retort 124. The heater H2 may be turned on toheat the furnace conduit 103. The binder trap cooler 604, e.g., the TECand/or the TEC fan, may be turned on. The binder trap cooler 604 may beconfigured to cool the binder trap 602 to facilitate the condensing orcoalescing of volatilized binder components present in the gaseouseffluent. In some aspect, operation of the binder trap cooler 604 mayallow the binder trap 602 to collect sufficient volatilized bindercomponents. Otherwise, if not enough binder component is collected, thenon-collected volatilized binder components may clog the vacuum pump 107or may flow through the vacuum pump 107 and into the catalytic convertersystem 110. Volatilized binder components in the catalytic convertersystem 110 may cause the enclosed catalyst to overheat. Non-collectedvolatilized binder components may also condense in the vacuum linebetween the binder trap 602 and the vacuum pump 107 and cause a clog.

The catalyst heater H3 and the air injector 109 may be turned on. Insome embodiments, the vacuum pump 107 may include a ballast to providean air injection from the oxidizing gas source 106. The oxidizing gasprovided by the vacuum pump 107 and/or the air injector 109 may be usedto partially or completely combust volatilized binder components presentin the gaseous effluent. In some embodiments, the gaseous effluentflowing out of the vacuum pump 107 exhaust and towards the catalyticconverter system 110 may include pump oil. The demister 108 may bepositioned adjacent to the vacuum pump 107 exhaust and may be configuredto remove and drain the pump oil back to the vacuum pump 107. Withoutthe demister 108, the pump oil present in the gaseous effluent may enterthe catalytic converter system 110, which may clog the catalyticconverter system 110 and cause the enclosed catalyst to overheat.Further, the continuous loss of the pump oil may cause the vacuum pump107 to run dry.

The furnace chamber 102 may be pumped down until the pressure at P2reaches a desired level. The desired level may vary depending on a typeof pump used in the furnace system 1100 and amount of insulationimplemented. In some embodiments, the desired level may be 1e⁻⁵ Torr. Insome embodiments, the desired level may be less than 50 mTorr. In someembodiments, the desired level may be less than 1 Torr. The controller116 may next initiate a system check before the furnace system 1100begins to heat up. As a pre-heat system check, an automated leak checkmay be performed on the furnace system 1100, including the binder trap602. The automated leak check may be performed by measuring the pressureat P2 and P7. As another pre-heat system check, TC8 may be used tomonitor the temperature of the furnace exhaust conduit 103, which isheated by heater H2. The sintering process may not continue if thetemperature at TC8 is below a predetermined minimum temperaturethreshold. In some embodiments, the predetermined minimum temperaturethreshold may be about 150 degrees Celsius. H2 may function to preventcondensation of high molecular weight species in the binder componentspresent in the gaseous effluent binder from condensing before desiredand clogging the furnace exhaust conduit 103. As another pre-heat systemcheck, TC10 may be used to monitor the temperature of the binder trap602. The sintering process may not continue if the temperature at TC10is above a predetermined maximum temperature threshold. In someembodiments, the predetermined minimum temperature threshold may beabout 15 degrees Celsius. In some embodiments, the temperature of thebinder trap 602 may be cooled to 10 degrees Celsius. As yet anotherpre-heat system check, TC13 may be used to monitor the temperature ofthe catalyst enclosure 111 a. The sintering process may not continue ifthe temperature at TC13 is not at a proper temperature, e.g., about225-400 degrees Celsius.

After the pre-heat system, heating may be initiated for the furnacesystem 1100. Once heating is started, V7 and V9 may remain open. V3 maybe opened, and the WC 113 may set the desired flow valve for the gasinlet conduit 115. Power may be applied to the heating elements, e.g.,heating elements 122 in the furnace chamber 102. During heating, TC1 andTC4 may be used to monitor and to control the ramp rate. Accordingly,the temperature within the furnace chamber 102 may be controlled suchthat it ramps at a desired rate. In some embodiments, the desired ratemay be 1-5 degrees per minute (deg/min).

Once the temperature monitored by TC1 and/or TC4 indicates that thetemperature of within the furnace chamber 102 is approaching a debindingtemperature, the temperature ramp rate may be slowed by the controller116. In the context of the current disclosure, a debinding temperatureis a temperature in which a thermal debinding process is performed. Forexample, a debinding temperature of 370 degrees Celsius may degradebinder components included in the part 126. In some embodiments, thedebinding temperature may depend on the type of binder componentsincluded in the part. For example, the debinding temperature of 370degrees Celsius may be for a polypropylene binder. In some embodiments,the debinding temperature may be between 350-400 degrees Celsius. Insome embodiments, the debinding temperature may be between 250-400degrees Celsius. In some embodiments, the debinding temperature maydepend on a temperature ramp rate of the furnace chamber 102. Forexample, the debinding temperature may be lower for a slower temperatureramp rate. Slower ramp rates may start to produce volatilized binder atlower temperatures.

Once the temperature within the furnace chamber 102 exceeds thedebinding temperature, the part 126 may begin to release volatilizedbinder components within the furnace chamber 102. As the thermaldebinding process begins, the furnace chamber temperature continues toramp at a slowed rate. For example, the ramp rate may be slowed from 3deg/min to 0.5 deg/min. Further, the binder trap 602 may begin tocollect volatilized binder components that are condensable and/orcoalescable. In some embodiments, the binder trap 602 may collect about20-60%, e.g., about 40%, of the total binder components included in thepart. The CO detector 112 may be used to continuously or intermittentlymonitor furnace system 1100 exhaust for the presence of CO. Thecontroller 116 may be configured to abort the sintering process if theCO level detected by the CO detector 112 surpasses a predeterminedthreshold.

During the sintering process, the temperature of the catalyst enclosure111 a may be continuously or intermittently monitored and controlled byusing the TC14. The monitoring and control may be designed to preventcatastrophic results in the catalytic converter system 110 in the eventa non-debound part is left in the furnace chamber 102. In the context ofthe current disclosure, a non-debound part refers to a part that has notbeen solvent debound or incompletely solvent debound prior to thethermal debinding performed in the furnace system 1100. Such non-deboundparts may contain a lot of primary binder, e.g., wax, that vaporize at arelatively low temperature and may then be consumed by the catalyticconvertor.

A substantially constant temperature may be maintained at TC14 duringthe sintering process. In some embodiments, the catalyst heater H3 mayheat the catalyst enclosure 111 a. TC13 may be used to measure thetemperature of the catalyst heater H3, and the setpoint of the catalystheater H3 may vary between T10 and T11. As the gaseous effluent flowsthrough the furnace system 1100 and into the catalyst enclosure 111 a,the catalyst reaction may generate heat. Accordingly, once the catalystreaction begins, the setpoint of the catalyst heater H3 may be lowered.That is, the catalyst heater H3 may not need to provide the same amountof heat to the catalyst enclosure 111 a due to heat generated by thecatalyst reaction.

If the temperature of the catalyst enclosure 111 a measured at TC14exceeds T3, the catalyst heater H3 may be turned off.

If the temperature of the catalyst enclosure 111 a measured at TC14exceeds T5, the furnace chamber temperature ramp may be paused. Thiswill decrease the amount of gaseous effluent generated in the furnacechamber 102. Accordingly, the amount of catalyst reaction may decrease,which may lower the temperature at TC14. Once the temperature at TC14becomes lower than T4, the furnace chamber temperature ramp may beresumed.

If the temperature measured at TC14 exceeds T6, then V7 may be closed.The closure of V7 may block off the flow of gaseous effluent to thecatalyst enclosure 111 a. Accordingly, the temperature at TC14 may startto decrease shortly thereafter. The furnace chamber temperature ramp mayremain paused. In order to recover from the furnace system 1100condition in which the temperature measured at TC14 exceeds T6, thefollowing procedures may subsequently be performed. When the temperatureat TC14 falls below T4, the V7 may be opened for a short period of time(set time) and then closed again. In some embodiments, the short periodof time may be less than 1 minute, e.g., 10-30 seconds. The flow ofgaseous effluent directed towards the catalyst enclosure 111 a duringthe short period of time may cause the temperature at TC14 to riseagain. For example, the temperature at TC14 may rise to exceed T5. As V7is closed, the temperature at TC14 may again fall below T4, at whichtime the V7 may be opened. The opening and closing of V7 may becontinued for increasingly longer opening times until the temperature atTC14 does not reheat over T5. At this point, V7 may be kept open and thesintering process may be continued.

If the temperature at TC14 exceeds T7, the sintering process may beaborted. If the temperature at TC13 exceeds T8, the sintering processmay be aborted.

The binder components included in the part 126 may be completelyvolatilized when the furnace temperature is sufficiently high, e.g.,about 500 degrees Celsius. In some embodiments, the sufficiently highfurnace temperature may vary depending on the binder components. Oncethe controller 116 determines that the binder components have beenvolatilized, the temperature ramp rate for the furnace chamber 102 maybe further increased. In some embodiments, the controller 116 maydetermine that the binder components have been volatilized when themeasured temperature at TC14 is lower than T3. In some instances, thismay indicate that there is no gaseous effluent going through thecatalytic converter system 110, thereby cooling the temperature at TC14to lower than T3, although, in practice, there may be residual binderthat exits furnace chamber 102 as furnace chamber is heated a bit more.In some embodiments, there may be an increase in the catalyst enclosure111 a temperature at TC 13 and pressure in the furnace chamber 102 oncethe temperature ramp rate for the furnace chamber is 102 is furtherincreased. This may be due to residual binder components remaining inthe parts or the fact that some binder components may have deposited inrelatively colder portions of the furnace chamber 102. The furtherincrease in the temperature ramp rate may volatize the remaining bindercomponents, thereby causing an increase in the catalyst enclosure 111 atemperature at TC 13 and pressure in the furnace chamber 102.

Once the binder components in the part 126 have been volatilized, thefurnace system 1100 may switch to a main sintering process (e.g.,densification) mode. In some embodiments, the temperature of the furnacechamber 102 may be initially increased to about 500-600 degrees Celsius,e.g., about 550 degrees Celsius. In the main sintering (e.g.,densification) process mode, V7 and V9 may be closed in order to sealthe binder trap 602. This may be because the binder trap 602 may nolonger be needed once all of the binder has been removed from the part126, and thus no additional volatilized binder component may be presentin the gaseous effluent.

With the binder trap 602 sealed, V8 may be opened, which may open up theisolation system bypass conduit 105. The isolation system bypass conduit105 may be connected to the inside of the furnace chamber 102 in aregion between the insulation and the furnace chamber wall. Accordingly,gaseous effluent remaining in the furnace chamber 102 may bypass thebinder trap 602 and may be directed to the catalytic converter system110.

The temperature for the furnace chamber 102 may be increased and gas maybe provided via the gas inlet conduit 115.

At higher temperatures (around 650 degrees Celsius), the furnace system1100 may begin to produce CO. In some embodiments, the CO may begenerated due to the reduction of metal oxides to metal by residualcarbon in the part 126. Any CO generated from the furnace chamber ispassed through the catalyst enclosure 111 a to ensure that the gaseouseffluent is safe.

If the catalyst enclosure 111 a cools sufficiently such that thetemperature at TC13 is lower than T1, the catalyst heater H3 may beturned back on.

Once the main sintering (e.g., densification) process is complete, theheating elements 122 may be turned off. In some embodiments, thecontroller 116 may determine that the main sintering process is completebased on a predetermined time duration at a measured main sinteringprocess temperature in the furnace chamber 102. In some embodiments, thecontroller 116 may determine that the main sintering process is completebased on various temperature measurements throughout the furnace system1100. The furnace chamber 102 may cool to an intermediate temperature ofabout 1000 degrees Celsius. The furnace chamber 102 may then bebackfilled by closing V8 and being filled with inert gas through the gasinlet conduit 115 until P9 reads a predetermined fill pressure, e.g.,about 930 Torr, or about 760 atm. In some embodiments, the predeterminedfill pressure may depend on the furnace chamber 102 material. Forexample, the predetermined fill pressure may be higher for a furnacechamber 102 made of stronger materials.

The furnace chamber 102 may continue to cool under pressure. Inert gasmay be periodically added via the gas inlet conduit 115 to maintain thepressure as the gas cools.

Eventually, the furnace chamber temperature as measured by TC4 may reacha safe opening temperature of less than 200 degrees Celsius. In someembodiments, the furnace chamber 102 may contain significant CO at thispoint in the process. In such embodiments, the furnace chamber 102 maybe pumped down by closing V3, MFC 113, and V100. V8 may be opened, andat least a portion of the gas containing CO may be pumped out anddirected to the catalytic converter system 110, where the CO may beconverted to CO₂.

The furnace chamber 102 may be left at vacuum pressure until a userdecides to open it. In some embodiments, an alarm or other indicator maysignal to the user that the furnace chamber is safe for opening. Oncethe user decides to open the furnace chamber 102, the furnace chambermay be backfilled to atmospheric pressure with room air through V11.Finally, the air pump 108, the vacuum pump 107, and the catalyst heaterH3 may be turned off. The user may then open the door to examine thesintered part.

In some embodiments, further processes may be performed to prevent thecatalyst in the catalytic converter system 110 from overheating. Forexample, catalyst overheating may be prevented or mitigated bymonitoring furnace chamber pressure at P2. If the pressure at P2 risesabove PV2, the furnace chamber heating rate may pause. When the pressureat P2 falls below PV1, the furnace chamber heating rate may resume. Insome instances, this may indicate a slowed generation rate ofvolatilized binder components. Accordingly, when the pressure at P2falls below PV1, this may indicate that there is less gaseous effluentfor the catalytic converter system 110 to react.

As another example, catalyst overheating may be prevented or mitigatedbased on air injection via the air injector 109. The air injector 109inject additional air to the catalytic converter system 110 if thecatalyst temperature exceeds a predetermined threshold. The additionalair flowing through the catalyst may remove excess heat and cool thecatalytic converter system 110. The additional air injection must bemeasured appropriately, as the additional air injection may reduce theresidence time of gaseous effluent in the catalytic converter system110. Unless properly monitored, reduced residence time may preventvolatilized binder components present in the gaseous effluent fromcomplete combustion.

As yet another example, catalyst overheating may be prevented ormitigated based on inert gas flow. This may not be particularlyapplicable to vacuum furnaces, but may be applicable to atmospherefurnaces. Gas inlet flow through the gas inlet conduit 115 may bestopped or decreased when the temperature at TC14 exceeds T5. Bydecreasing the inlet flow, the outlet flow may also be decreased. Theflow may resume to the previous rate when the temperature at TC14 fallsbelow T4.

In an aspect, the controller 116 may automatically control the furnacesystems described herein based on pre-set schedules and/or on userinput. In some embodiments, the control of the furnace systems describedherein may also be manual and performed by a user. In some embodiments,the furnace systems described herein also include a manual overrideand/or emergency stop such that a user may configure and/or stop aprocess performed within the furnace system.

The furnace chamber 102 in any of the embodiments described herein mayinclude the one or more heating elements 122 and one or more temperaturemeasurement devices, such as a thermocouple. The furnace system in anyof the embodiments described herein may include one or more oxygengetters configured to prevent back diffusion of oxidizing gas and/orvarious other types of gas.

FIG. 12A illustrates an exemplary system 1200 for forming a printedobject, of which the furnace systems described herein may be a part of.System 1200 may include a three-dimensional (3D) printer, for example, ametal 3D printing subsystem 1202, and one or more treatment site(s), forexample, a debinding subsystem 1204 and a furnace subsystem 1206 fortreating the green part after printing. In some embodiments, the furnacesubsystem 1206 may be the furnace system in any of the embodimentsdescribed herein. Metal 3D printing subsystem 1202 may be used to forman object from a build material, for example, by depositing successivelayers of the build material onto a build plate. The build material mayinclude metal powder and at least one binder material. In someembodiments, the build material may include a primary binder material(e.g., a wax) and a secondary binder material (e.g., a polymer).

Debinding subsystem 1204 may be configured to treat the printed objectby performing a first debinding process, in which the primary bindermaterial may be removed. In some embodiments, the first debindingprocess may be a chemical debinding process, as will be described infurther detail with reference to FIG. 12C. In such embodiments, theprimary binder material may dissolve in a debinding fluid while thesecondary binder material remains, holding the metal particles in placein their printed form.

In other embodiments, the first debinding process may comprise a thermaldebinding process. In such embodiments, the primary binder material mayhave a vaporization temperature lower than that of the secondary bindermaterial. The debinding subsystem 1204 may be configured to heat thedeposited build material to a temperature at or above the vaporizationtemperature of the primary binder material and below the vaporizationtemperature of the secondary binder material such that the primarybinder material is removed from the printed part. In alternativeembodiments, the furnace subsystem 1206 rather than a separate heatingdebinding subsystem 1204 may be configured to perform the firstdebinding process. For example, the furnace subsystem 1206 may beconfigured to heat the deposited build material to a temperature at orabove the vaporization temperature of the primary binder material andbelow the vaporization temperature of the secondary binder material suchthat the primary binder material is removed from the deposited buildmaterial.

Furnace subsystem 1206 may be configured to treat the printed object byperforming a secondary debinding process (or also a primary debindingprocess, as in the alternative embodiment described above), in which thesecondary binder material and/or any remaining primary binder materialmay be removed from the printed part. In some embodiments, the secondarydebinding process may comprise a thermal debinding process, in which thefurnace subsystem 1206 may be configured to heat the part to atemperature at or above the vaporization temperature of the secondarybinder material to remove the secondary binder material. The furnacesubsystem 1206 may then heat the part to a temperature just below themelting point of the metal powder to sinter the metal powder and todensify the metal powder into a solid metal part.

As shown in FIG. 12A, system 1200 may also include a user interface1210, which may be operatively coupled to one or more components, forexample, to metal 3D printing subsystem 1202, debinding subsystem 1204,and furnace subsystem 1206, etc. In some embodiments, user interface1210 may be a remote device (e.g., a computer, a tablet, a smartphone, alaptop, etc.) or an interface incorporated into system 1200, e.g., onone or more of the components. User interface 1210 may be wired orwirelessly connected to one or more of metal 3D printing subsystem 1202,debinding subsystem 1204, and/or furnace subsystem 1206. System 1200 mayalso include a control subsystem 1216, which may be included in userinterface 1210, or may be a separate element.

Metal 3D printing subsystem 1202, debinding subsystem 1204, furnacesubsystem 1206, user interface 1210, and/or control subsystem 1216 mayeach be connected to the other components of system 1200 directly or viaa network 1212. Network 1212 may include the Internet and may providecommunication through one or more computers, servers, and/or handheldmobile devices, including the various components of system 1200. Forexample, network 1212 may provide a data transfer connection between thevarious components, permitting transfer of data including, e.g., partgeometries, printing material, one or more support and/or supportinterface details, printing instructions, binder materials, heatingand/or sintering times and temperatures, etc., for one or more parts orone or more parts to be printed.

Moreover, network 1212 may be connected to a cloud-based application1214, which may also provide a data transfer connection between thevarious components and cloud-based application 1214 in order to providea data transfer connection, as discussed above. Cloud-based application1214 may be accessed by a user in a web browser, and may include variousinstructions, applications, algorithms, methods of operation,preferences, historical data, etc., for forming the part or object to beprinted based on the various user-input details. Alternatively oradditionally, the various instructions, applications, algorithms,methods of operation, preferences, historical data, etc., may be storedlocally on a local server (not shown) or in a storage and/or processingdevice within or operably coupled to one or more of metal 3D printingsubsystem 1202, debinding subsystem 1204, sintering furnace subsystem1206, user interface 1210, and/or control subsystem 1216. In thisaspect, metal 3D printing subsystem 1202, debinding subsystem 1204,furnace subsystem 1206, user interface 1210, and/or control subsystem1216 may be disconnected from the Internet and/or other networks, whichmay increase security protections for the components of system 1200. Ineither aspect, an additional controller (not shown) may be associatedwith one or more of metal 3D printing subsystem 1202, debindingsubsystem 1204, and furnace subsystem 1206, etc., and may be configuredto receive instructions to form the printed object and to instruct oneor more components of system 1200 to form the printed object.

FIG. 12B is a block diagram of a metal 3D printing subsystem 1202according to one embodiment. The metal 3D printing subsystem 1202 mayextrude build material 1224 to form a three-dimensional part. Asdescribed above, the build material may include a mixture of metalpowder and binder material. For example, the build material may includeany combination of metal powder, plastics, wax, ceramics, polymers,among others. In some embodiments, the build material 1224 may come inthe form of a rod comprising a predetermined composition of metal powderand one or more binder components (e.g., a primary and a secondarybinder).

Metal 3D printing subsystem 1202 may include an extrusion assembly 1226comprising an extrusion head 1232. Metal 3D printing subsystem 1202 mayinclude an actuation assembly 1228 configured to propel the buildmaterial 1224 into the extrusion head 1232. For example, the actuationassembly 1228 may be configured to propel the build material 1224 in arod form into the extrusion head 1232. In some embodiments, the buildmaterial 1224 may be continuously provided from the feeder assembly 1222to the actuation assembly 1228, which in turn propels the build material1224 into the extrusion head 1232. In some embodiments, the actuationassembly 1228 may employ a linear actuation to continuously grip and/orpush the build material 1224 from the feeder assembly 1222 towards theextrusion head 1232.

In some embodiments, the metal 3D printing subsystem 1202 includes aheater 1234 configured to generate heat 1236 such that the buildmaterial 1224 propelled into the extrusion head 1232 may be heated to aworkable state. In some embodiments, the heated build material 1224 maybe extruded through one or more nozzle 1233 to extrude workable buildmaterial 1242 onto a build plate 1240. It is understood that the heater1234 is an exemplary device for generating heat 1236, and that heat 1236may be generated in any suitable way, e.g., via friction of the buildmaterial 1224 interacting with the extrusion assembly 1226, inalternative embodiments.

In some embodiments, the metal 3D printing subsystem 1202 comprises acontroller 1238. The controller 1238 may be configured to position theone or more nozzles 1233 along an extrusion path relative to the buildplate 1240 such that the workable build material is deposited on thebuild plate 1240 to fabricate a three dimensional printed object 1230.The controller 1238 may be configured to manage operation of the metal3D printing subsystem 1202 to fabricate the printed object 1230according to a three-dimensional model. In some embodiments, thecontroller 1238 may be remote or local to the metallic printingsubsystem 1202. The controller 1238 may be a centralized or distributedsystem. In some embodiments, the controller 1238 may be configured tocontrol a feeder assembly 1222 to dispense the build material 1224. Insome embodiments, the controller 1238 may be configured to control theextrusion assembly 1226, e.g., the actuation assembly 1228, the heater1234, the extrusion head 1232, and/or the one or more nozzle 1233. Insome embodiments the controller 1238 may be included in the controlsubsystem 1216.

FIG. 12C depicts a block diagram of a debinder subsystem 1204 fordebinding a printed object 1230 according to one embodiment. Thedebinder subsystem 1204 may include a process chamber 1250, into whichthe printed object 1230 may be inserted for a first debinding process.In some embodiments, the first debinding process may be a chemicaldebinding process. In such embodiments, the debinder subsystem 1204 mayinclude a storage chamber 1256 to store a volume of debinding fluid,e.g., a solvent, for use in the first debinding process. The storagechamber 1256 may comprise a port which may be used to fill, refill,and/or drain the storage chamber 1256 with the debinding fluid. In someembodiments, the storage chamber 1256 may be removably attached to thedebinder subsystem 1204. In such embodiments, the storage chamber 1256may be removed and replaced with a replacement storage chamber (notshown in FIG. 1C) to replenish the debinding fluid in the debindingsubsystem 1204. In some embodiments, the storage chamber 1256 may beremoved, refilled with debinding fluid, and reattached to the debindingsubsystem 1204.

The debinding fluid contained in the storage chamber 1256 may bedirected to the process chamber 1250 containing the inserted printedobject 1230. In some embodiments, the build material that the printedobject 1230 is formed of may include a primary binder material and asecondary binder material. In some embodiments, the printed object 1230in the process chamber 1250 may be submerged in the debinding fluid fora predetermined period of time. In such embodiments, the primary bindermaterial may dissolve in the debinding fluid while the secondary bindermaterial stays intact.

In some embodiments, the debinding fluid containing the dissolvedprimary binder material (hereinafter referred to as “used debindingfluid”) may be directed to a distill chamber 1252. For example, afterthe first debinding process, the process chamber 1250 may be drained ofthe used debinding fluid, and the used debinding fluid may be directedto the distill chamber 1252. In some embodiments, the distill chamber1252 may be configured to distill the used debinding fluid. In someembodiments, the debinding subsystem 1204 may further include a wastechamber 1254 fluidly coupled to the distill chamber 1252. In suchembodiments, the waste chamber may collect waste accumulated in thedistill chamber 1252 as a result of the distillation. In someembodiments, the waste chamber 1254 may be removably attached to thedebinding subsystem 1204 such that the waste chamber 1254 may be removedand replaced after a number of distillation cycles. In some embodiments,the debinding subsystem 1204 may include a condenser 1258 configured tocondense vaporized used debinding fluid from the distill chamber 1252and return the debinding fluid back to the storage chamber 1256.

FIG. 13A illustrates another exemplary system 1300 for forming a printedobject, of which the furnace systems described herein may be included.System 1300 may include a printer, for example, a binder jet fabricationsubsystem 1302, and a treatment site(s), for example, a de-powderingsubsystem 1304 and a furnace subsystem 1306. In some embodiments, thefurnace subsystem 1306 may be the furnace system in any of theembodiments described herein. Binder jet fabrication subsystem 1302 maybe used to form an object from a build material, for example, bydelivering successive layers of build material and binder material to abuild plate. As shown in FIG. 13A, a build box subsystem 1308 may bemovable and may be selectively positioned in one or more of binder jetfabrication subsystem 1302, de-powdering subsystem 1304, and furnacesubsystem 1306. For example, build box subsystem 1308 may be coupled orcouplable to a movable assembly. Alternatively, a conveyor (not shown)may help transport the object between portions of system 1300.

The build material may be a bulk metallic powder delivered and spread insuccessive layers. The binder material may be, for example, a polymericliquid that may be deposited onto and may be absorbed into layers of thebuild material. One or more of binder jet fabrication subsystem 1302,de-powdering subsystem 1304, and furnace subsystem 1306 may include ashaping station to shape the printed object and a debinding station totreat the printed object to remove a binder material from the buildmaterial. Furnace subsystem 1306 may heat and/or sinter the buildmaterial of the printed object. System 1300 may also include a userinterface 1310, which may be operatively coupled to one or morecomponents, for example, to binder jet fabrication subsystem 1302,de-powdering subsystem 1304, and furnace subsystem 1306, etc. In someembodiments, user interface 1310 may be a remote device (e.g., acomputer, a tablet, a smartphone, a laptop, etc.). User interface 1310may be wired or wirelessly connected to one or more of binder jetfabrication subsystem 1302, de-powdering subsystem 1304, and furnacesubsystem 1306. System 1300 may also include a control subsystem 1316,which may be included in user interface 1310, or may be a separateelement.

Binder jet fabrication subsystem 1302, de-powdering subsystem 1304,furnace subsystem 1306, user interface 1310, and/or control subsystem1316 may each be connected to the other components of system 1300directly or via a network 1312. Network 1312 may include the Internetand may provide communication through one or more computers, servers,and/or handheld mobile devices, including the various components ofsystem 1300. For example, network 1312 may provide a data transferconnection between the various components, permitting transfer of dataincluding, e.g., geometries, the printing material, one or more supportand/or support interface details, binder materials, heating and/orsintering times and temperatures, etc., for one or more parts or one ormore parts to be printed.

Moreover, network 1312 may be connected to a cloud-based application1314, which may also provide a data transfer connection between thevarious components and cloud-based application 1314 in order to providea data transfer connection, as discussed above. Cloud-based application1314 may be accessed by a user in a web browser, and may include variousinstructions, applications, algorithms, methods of operation,preferences, historical data, etc., for forming the part or object to beprinted based on the various user-input details. Alternatively oradditionally, the various instructions, applications, algorithms,methods of operation, preferences, historical data, etc., may be storedlocally on a local server (not shown) or in a storage and/or processingdevice within or operably coupled to one or more of binder jetfabrication subsystem 1302, de-powdering subsystem 1304, furnacesubsystem 1306, user interface 1310, and/or control subsystem 1316. Inthis aspect, binder jet fabrication subsystem 1302, de-powderingsubsystem 1304, furnace subsystem 1306, user interface 1310, and/orcontrol subsystem 1316 may be disconnected from the Internet and/orother networks, which may increase security protections for thecomponents of system 1300. In either aspect, an additional controller(not shown) may be associated with one or more of binder jet fabricationsubsystem 1302, de-powdering subsystem 1304, and furnace subsystem 1306,etc., and may be configured to receive instructions to form the printedobject and to instruct one or more components of system 1300 to form theprinted object.

FIG. 13B illustrates an exemplary binder jet fabrication subsystem 1302operating in conjunction with build box subsystem 1308. Binder jetfabrication subsystem 1302 may include a powder supply 1320, a spreader1322 (e.g., a roller) configured to be movable across powder bed 1324 ofbuild box subsystem 1308, a print head 1326 movable across powder bed1324, and a controller 1328 in electrical communication (e.g., wireless,wired, Bluetooth, etc.) with print head 1326. Powder bed 1324 maycomprise powder particles, for example, micro-particles of a metal,micro-particles of two or more metals, or a composite of one or moremetals and other materials.

Spreader 1322 may be movable across powder bed 1324 to spread a layer ofpowder, from powder supply 1320, across powder bed 1324. Print head 1326may comprise a discharge orifice 1330 and, in certain implementations,may be actuated to dispense a binder material 1332 (e.g., throughdelivery of an electric current to a piezoelectric element in mechanicalcommunication with binder material 1332) through discharge orifice 1330to the layer of powder spread across powder bed 1324. In someembodiments, the binder material 1332 may be one or more fluidsconfigured to bind together powder particles.

In operation, controller 1328 may actuate print head 1326 to deliverbinder material 1332 from print head 1326 to each layer of the powder ina pre-determined two-dimensional pattern, as print head 1326 movesacross powder bed 1324. In embodiments, the movement of print head 1326,and the actuation of print head 1326 to deliver binder material 1332,may be coordinated with movement of spreader 1322 across print bed 1324.For example, spreader 1322 may spread a layer of the powder across printbed 1324, and print head 1326 may deliver the binder in apre-determined, two-dimensional pattern, to the layer of the powderspread across print bed 1324, to form a layer of one or morethree-dimensional objects 1334. These steps may be repeated (e.g., withthe pre-determined two-dimensional pattern for each respective layer) insequence to form subsequent layers until, ultimately, the one or morethree-dimensional objects 1334 are formed in powder bed 1324.

Although the example embodiment depicted in FIG. 13B depicts a singleobject 1334 being printed, it should be understood that the powder printbed 1324 may include more than one object 1334 in embodiments in whichmore than one object 1334 is printed at once. Further, the powder printbed 1324 may be delineated into two or more layers, stacked vertically,with one or more objects disposed within each layer.

An example binder jet fabrication subsystem 1302 may comprise a powdersupply actuator mechanism 1336 that elevates powder supply 1320 asspreader 1322 layers the powder across print bed 1324. Similarly, buildbox subsystem 1308 may comprise a build box actuator mechanism 1338 thatlowers powder bed 1324 incrementally as each layer of powder isdistributed across powder bed 1324.

In another example embodiment, layers of powder may be applied to powderprint bed 1324 by a hopper followed by a compaction roller. The hoppermay move across powder print bed 1324, depositing powder along the way.The compaction roller may be configured to follow the hopper, spreadingthe deposited powder to form a layer of powder.

For example, FIG. 13C illustrates another binder jet fabricationsubsystem 1302′ operating in conjunction with a build box subsystem1308′. In this aspect, binder jet fabrication subsystem 1302′ mayinclude a powder supply 1320′ in a metering apparatus, for example, ahopper 1321. Binder jet subsystem 1302′ may also include one or morespreaders 1322′ (e.g., one or more rollers) configured to be movableacross powder bed 1324′ of build box subsystem 1308′, a print head 1326′movable across powder bed 1324′, and a controller 1328′ in electricalcommunication (e.g., wireless, wired, Bluetooth, etc.) with one or moreof hopper 1321, spreaders 1322′, and print head 1326′. Powder bed 1324′may comprise powder particles, for example, micro-particles of a metal,micro-particles of two or more metals, or a composite of one or moremetals and other materials.

Hopper 1321 may be any suitable metering apparatus configured to meterand/or deliver powder from powder supply 1320′ onto a top surface 1323of powder bed 1324′. Hopper 1321 may be movable across powder bed 1324′to deliver powder from powder supply 1320′ onto top surface 1323. Thedelivered powder may form a pile 1325 of powder on top surface 1323.

The one or more spreaders 1322′ may be movable across powder bed 1324′downstream of hopper 1321 to spread powder, e.g., from pile 1325, acrosspowder bed 1324. The one or more spreaders 1322′ may also compact thepowder on top surface 1323. In either aspect, the one or more spreaders1322′ may form a layer 1327 of powder. The aforementioned powderdelivery and spreading steps may be successively performed in order toform a plurality of layers 1329 of powder. Additionally, although twospreaders 1322′ are shown in FIG. 13C, binder jet fabrication subsystem1302′ may include one, three, four, etc. spreaders 1322′.

Print head 1326′ may comprise one or more discharge orifices 1330′ and,in certain implementations, may be actuated to dispense a bindermaterial 1332′ (e.g., through delivery of an electric current to apiezoelectric element in mechanical communication with binder material1332′) through discharge orifice 1330′ to the layer of powder spreadacross powder bed 1324′. In some embodiments, the binder material 1332′may be one or more fluids configured to bind together powder particles.

In operation, controller 1328′ may actuate print head 1326′ to deliverbinder material 1332′ from print head 1326′ to each layer 1327 of thepowder in a pre-determined two-dimensional pattern, as print head 1326′moves across powder bed 1324′. As shown in FIG. 13C, controller 1328′may be in communication with hopper 1321 and/or the one or morespreaders 1322′ as well, for example, to actuate the movement of hopper1321 and the one or more spreaders 1322′ across powder bed 1324′.Additionally, controller 1328′ may control the metering and/or deliveryof powder by hopper 1321 from powder supply 1320 to top surface 1323 ofpowder bed 1324′. In embodiments, the movement of print head 1326′, andthe actuation of print head 1326′ to deliver binder material 1332′, maybe coordinated with movement of hopper 1321 and the one or morespreaders 1322′ across print bed 1324′. For example, hopper 1321 maydeliver powder to print bed 1324, and spreader 1322′ may spread a layerof the powder across print bed 1324. Then, print head 1326 may deliverthe binder in a pre-determined, two-dimensional pattern, to the layer ofthe powder spread across print bed 1324′, to form a layer of one or morethree-dimensional objects 1334′. These steps may be repeated (e.g., withthe pre-determined two-dimensional pattern for each respective layer) insequence to form subsequent layers until, ultimately, the one or morethree-dimensional objects 1334′ are formed in powder bed 1324′.

Although the example embodiment depicted in FIG. 13C depicts a singleobject 1334′ being printed, it should be understood that the powderprint bed 1324′ may include more than one object 1334′ in embodiments inwhich more than one object 1334′ is printed at once. Further, the powderprint bed 1324′ may be delineated into two or more layers 1327, stackedvertically, with one or more objects disposed within each layer.

As in FIG. 13B, build box subsystem 1308′ may comprise a build boxactuator mechanism 1338′ that lowers powder bed 1324′ incrementally aseach layer 1327 of powder is distributed across powder bed 1324′.Accordingly, hopper 1321, the one or more spreaders 1322′, and printhead 1326′ may traverse build box subsystem 1308′ at a pre-determinedheight, and build box actuator mechanism 1338′ may lower powder bed 1324to form object 1334′.

Although not shown, binder jet fabrication subsystems 1302, 1302′ mayinclude a coupling interface that may facilitate the coupling and/oruncoupling of the build box subsystems 1308, 1308′ with the binder jetfabrication subsystems 1302, 1302′, respectively. The coupling interfacemay comprise one or more of (i) a mechanical aspect that provides forphysical engagement, and/or (ii) an electrical aspect that supportselectrical communication between the build box subsystem 1308, 1308′ tothe binder jet fabrication subsystem 1302, 1302′.

As shown in FIG. 14, a device 1400 used for performing the variousembodiments of the present disclosure (e.g., the controller 116, thecontroller subsystem 1216, the controller subsystem 1316, the variousfurnace systems, system 1200, and system 1300 disclosed herein, and/orany other computer system or user terminal for performing the variousembodiments of the present disclosure) may include a central processingunit (CPU) 1420. CPU 1420 may be any type of processor device including,for example, any type of special purpose or general-purposemicroprocessor device. As will be appreciated by persons skilled in therelevant art, CPU 1420 also may be a single processor in amulti-core/multiprocessor system, such system operating alone, or in acluster of computing devices operating in a cluster or a server farm.CPU 1420 may be connected to a data communication infrastructure 1410,for example, a bus, message queue, network, or multi-coremessage-passing scheme.

A device 1400 (e.g., the controller 116, the controller subsystem 1216,the controller subsystem 1316, the various furnace systems, system 1200,and system 1300 disclosed herein, and/or any other computer system oruser terminal for performing the various embodiments of the presentdisclosure) may also include a main memory 1440, for example, randomaccess memory (RAM), and may also include a secondary memory 1430.Secondary memory 1430, e.g., a read-only memory (ROM), may be, forexample, a hard disk drive or a removable storage drive. Such aremovable storage drive may comprise, for example, a floppy disk drive,a magnetic tape drive, an optical disk drive, a flash memory, or thelike. The removable storage drive in this example may read from and/orwrite to a removable storage unit in a well-known manner. The removablestorage unit may comprise a floppy disk, magnetic tape, optical disk,etc., which is read by and written to by the removable storage drive. Aswill be appreciated by persons skilled in the relevant art, such aremovable storage unit generally includes a computer usable storagemedium having stored therein computer software and/or data.

In alternative implementations, secondary memory 1430 may include othersimilar means for allowing computer programs or other instructions to beloaded into device 1400. Examples of such means may include a programcartridge and cartridge interface (such as that found in video gamedevices), a removable memory chip (such as an EPROM, or PROM) andassociated socket, and other removable storage units and interfaces,which allow software and data to be transferred from a removable storageunit to device 1400.

A device 1400 may also include a communications interface (“COM”) 1460.Communications interface 1460 may allow software and data to betransferred between device 1400 and external devices. Communicationsinterface 1460 may include a modem, a network interface (such as anEthernet card), a communications port, a PCMCIA slot and card, or thelike. Software and data transferred via communications interface 1460may be in the form of signals, which may be electronic, electromagnetic,optical, or other signals capable of being received by communicationsinterface 1460. These signals may be provided to communicationsinterface 1460 via a communications path of device 1400, which may beimplemented using, for example, wire or cable, fiber optics, a phoneline, a cellular phone link, an RF link, a wireless connection (e.g.,Bluetooth connection, wireless local are network (WLAN) connection, andcellular network connection) or other communications channels.

The hardware elements, operating systems, and programming languages ofsuch equipment are conventional in nature, and it is presumed that thoseskilled in the art are adequately familiar therewith. A device 1400 alsomay include input and output ports 1450 to connect with input and outputdevices such as keyboards, mice, touchscreens, monitors, displays, etc.Of course, the various server functions may be implemented in adistributed fashion on a number of similar platforms, to distribute theprocessing load. Alternatively, the servers may be implemented byappropriate programming of one computer hardware platform.

The systems, apparatuses, devices, and methods disclosed herein aredescribed in detail by way of examples and with reference to thefigures. The examples discussed herein are examples only and areprovided to assist in the explanation of the apparatuses, devices,systems, and methods described herein. None of the features orcomponents shown in the drawings or discussed below should be taken asmandatory for any specific implementation of any of these theapparatuses, devices, systems, or methods unless specifically designatedas mandatory. For ease of reading and clarity, certain components,modules, or methods may be described solely in connection with aspecific figure. In this disclosure, any identification of specifictechniques, arrangements, etc., are either related to a specific examplepresented or are merely a general description of such a technique,arrangement, etc. Identifications of specific details or examples arenot intended to be, and should not be, construed as mandatory orlimiting unless specifically designated as such. Any failure tospecifically describe a combination or sub-combination of componentsshould not be understood as an indication that any combination orsub-combination is not possible. It will be appreciated thatmodifications to disclosed and described examples, arrangements,configurations, components, elements, apparatuses, devices, systems,methods, etc., can be made and may be desired for a specificapplication. Also, for any methods described, regardless of whether themethod is described in conjunction with a flow diagram, it should beunderstood that unless otherwise specified or required by context, anyexplicit or implicit ordering of steps performed in the execution of amethod does not imply that those steps must be performed in the orderpresented but instead may be performed in a different order or inparallel.

Throughout this disclosure, references to components or modulesgenerally refer to items that logically can be grouped together toperform a function or group of related functions. Like referencenumerals are generally intended to refer to the same or similarcomponents. Components and modules can be implemented in software,hardware, or a combination of software and hardware. The term “software”is used expansively to include not only executable code, for examplemachine-executable or machine-interpretable instructions, but also datastructures, data stores and computing instructions stored in anysuitable electronic format, including firmware, and embedded software.

It is intended that the specification and examples be considered asexemplary only, with a true scope and spirit of the disclosure beingindicated by the following claims.

What is claimed is:
 1. A furnace system, comprising: a furnace chamberdefining an interior region, wherein the furnace chamber is configuredto maintain an atmosphere substantially free of oxygen within theinterior region; an outlet fluidly coupled to the furnace chamber forremoval of an exhaust gas from the furnace chamber; a conduit fluidlycoupled to the outlet; an oxygen injector fluidly coupled to theconduit, wherein the oxidizing injector is positioned downstream of thefurnace chamber and is configured to introduce an oxidizing gas into theexhaust gas; an isolation system fluidly coupled to the conduit betweenthe furnace chamber and the oxygen injector, wherein the isolationsystem is configured to prevent a backflow of the oxidizing gas into thefurnace chamber; and a catalyst enclosure comprising an oxidizingcatalyst, wherein the catalyst enclosure is configured to receive amixture of the exhaust gas and the oxidizing gas.
 2. The furnace systemof claim 1, wherein the isolation system comprises a pump configured todirect the exhaust gas through the isolation system and towards thecatalyst enclosure, wherein the pump is at least one of a vacuum pump, alobe pump, a diaphragm pump, a piston pump, or a venturi pump.
 3. Thefurnace system of claim 2, further comprising: a demister positionedbetween the vacuum pump and the catalyst enclosure, wherein the demisteris configured to remove at least a portion of fluid present in theexhaust gas directed towards the catalyst enclosure, and wherein thedemister is fluidly connected to the vacuum pump such that the removedfluid is drained back to the vacuum pump.
 4. The furnace system of claim1, wherein the isolation system comprises a check valve configured toprevent the backflow of the oxidizing gas into the furnace chamber. 5.The furnace system of claim 1, wherein the isolation system comprises aproportional valve configured to prevent the backflow of the oxidizinggas into the furnace chamber, wherein the proportional valve is at leastone of a proportional butterfly valve or a proportional solenoid valve.6. The furnace system of claim 1, wherein the isolation system comprisesa porous plug configured to prevent the backflow of the oxidizing gasinto the furnace chamber.
 7. The furnace system of claim 1, furthercomprising a heater operably coupled to the conduit, and wherein theconduit is configured to be adjustably heated.
 8. The furnace system ofclaim 7, wherein the isolation system comprises a liquid bubblerconfigured to prevent the backflow of the oxidizing gas into the furnacechamber and to collect at least a portion of a component present in theexhaust gas.
 9. The furnace system of claim 8, wherein the liquidbubbler comprises a connecting conduit with a first end and a secondend, a first chamber fluidly connected to the conduit and the first endof the connecting conduit, and a second chamber fluidly connected to anoutlet conduit and the second end of the connecting conduit, wherein thefirst end of the connecting conduit is located within the first chamber,and the second end of the connecting conduit is located within thesecond chamber, and the second chamber is at least partially filled witha liquid such that a top surface of the liquid is above the second endof the connecting conduit, and wherein the liquid bubbler is configuredto sequentially receive the exhaust gas through the first chamber, theconnecting conduit, the second chamber, and the outlet conduit.
 10. Afurnace system, comprising: a furnace chamber defining an interiorregion, wherein the furnace chamber is configured to maintain anatmosphere substantially free of oxygen within the interior region; anoutlet fluidly coupled to the furnace chamber for removal of an exhaustgas from the furnace chamber; a binder trap system fluidly coupled tothe outlet; an isolation system fluidly coupled to the binder trapsystem, wherein the isolation system is positioned downstream of thebinder trap system and is configured to prevent a backflow of anoxidizing gas into the furnace chamber; a catalyst enclosure comprisingan oxidizing catalyst, wherein the catalyst enclosure is positioneddownstream of the isolation system and is configured to receive amixture of the exhaust gas and the oxidizing gas; and an oxygen injectorfluidly coupled to at least one of the isolation system or the catalystenclosure, wherein the oxidizing injector is positioned downstream ofthe furnace chamber and is configured to introduce the oxidizing gasinto the exhaust gas.
 11. The furnace system of claim 10, wherein theisolation system comprises at least one of a check valve, a proportionalvalve, a pump, or a porous plug.
 12. The furnace system of claim 10,wherein the binder trap system comprises a binder trap cooler configuredto adjust a temperature of the binder trap.
 13. The furnace system ofclaim 10, further comprising: a binder trap system bypass conduitfluidly coupled to the outlet downstream of the binder trap system andto the isolation system upstream of the binder trap system, wherein thebinder trap system bypass conduit is configured to direct the exhaustgas to bypass the binder trap system.
 14. The furnace system of claim13, wherein the bypass conduit includes at least one valve configured tooptionally open the bypass conduit to allow the exhaust gas to bypassthe binder trap system or to close the bypass conduit to allow theexhaust gas to flow through the binder trap system.
 15. A furnacesystem, comprising: a furnace chamber defining an interior region,wherein the furnace chamber is configured to maintain an atmospheresubstantially free of oxygen within the interior region; an outletfluidly coupled to the furnace chamber for removal of an exhaust gasfrom the furnace chamber; an isolation system fluidly coupled to theoutlet, wherein the isolation system is configured to prevent a backflowof an oxidizing gas into the furnace chamber; a binder cracking systemfluidly coupled to the isolation system, wherein the binder crackingsystem is positioned downstream of the isolation system; a catalystenclosure comprising an oxidizing catalyst, wherein the catalystenclosure is positioned downstream of the isolation system and isconfigured to receive a mixture of the exhaust gas and the oxidizinggas; and an oxygen injector fluidly coupled to at least one of theisolation system or the catalyst enclosure, wherein the oxidizinginjector is positioned downstream of the furnace chamber and isconfigured to introduce the oxidizing gas into the exhaust gas.
 16. Thefurnace system of claim 15, wherein isolation system comprises a checkvalve configured to prevent a backflow of the oxidizing gas into thefurnace chamber.
 17. The furnace system of claim 15, wherein the bindercracking system comprises an enclosure substantially free of oxygen anda heater configured to heat the enclosure.
 18. The furnace system ofclaim 17, wherein the enclosure contains a catalyst configured to reactwith at least the portion of a component of the exhaust gas.
 19. Thefurnace system of claim 17, wherein the binder cracking system furthercomprises a steam source and a flame arrestor positioned downstream ofthe enclosure.
 20. The furnace system of claim 17, wherein the isolationsystem further comprises a venturi pump positioned downstream of thebinder cracking system and is configured to prevent a backflow of theoxidizing gas into the furnace chamber.